Configuration sharing from SDK client to credentials provider

Created a LambdaClient as follows:

`

httpClientBuilder =
ApacheHttpClient.builder()
.proxyConfiguration(
proxyConfig
.endpoint(URI.create("http://myproxy.com:8080"))
.username("username")
.password("password")
.build());

client =
LambdaClient.builder()
.httpClientBuilder(httpClientBuilder)
.region(region)
.build();
`

In SdkDefaultClientBuilder being called internally from DefaultStsClientBuilder, I see that the httpClient is being created with an empty proxyConfiguration.

## Expected Behavior
Sts should use the same proxyConfigration as the one I passed to the LambdaClient.

## Current Behavior
Proxy is not used, and thus the host is not resolvable.

`
software.amazon.awssdk.core.exception.SdkClientException: Unable to execute HTTP request: sts.amazonaws.com
at software.amazon.awssdk.core.exception.SdkClientException$BuilderImpl.build(SdkClientException.java:97)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage$RetryExecutor.handleThrownException(RetryableStage.java:164)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage$RetryExecutor.execute(RetryableStage.java:117)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage.execute(RetryableStage.java:67)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage.execute(RetryableStage.java:47)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:205)
at software.amazon.awssdk.core.internal.http.StreamManagingStage.execute(StreamManagingStage.java:56)
at software.amazon.awssdk.core.internal.http.StreamManagingStage.execute(StreamManagingStage.java:41)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:205)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:205)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ExecutionFailureExceptionReportingStage.execute(ExecutionFailureExceptionReportingStage.java:37)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ExecutionFailureExceptionReportingStage.execute(ExecutionFailureExceptionReportingStage.java:25)
at software.amazon.awssdk.core.internal.http.AmazonSyncHttpClient$RequestExecutionBuilderImpl.execute(AmazonSyncHttpClient.java:272)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler.invoke(BaseSyncClientHandler.java:90)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler.execute(BaseSyncClientHandler.java:102)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler.execute(BaseSyncClientHandler.java:67)
at software.amazon.awssdk.core.client.handler.SdkSyncClientHandler.execute(SdkSyncClientHandler.java:44)
at software.amazon.awssdk.awscore.client.handler.AwsSyncClientHandler.execute(AwsSyncClientHandler.java:53)
at software.amazon.awssdk.services.sts.DefaultStsClient.assumeRole(DefaultStsClient.java:239)
at software.amazon.awssdk.services.sts.auth.StsAssumeRoleCredentialsProvider.getUpdatedCredentials(StsAssumeRoleCredentialsProvider.java:68)
at software.amazon.awssdk.services.sts.auth.StsCredentialsProvider.updateSessionCredentials(StsCredentialsProvider.java:68)
at software.amazon.awssdk.utils.cache.CachedSupplier.refreshCache(CachedSupplier.java:133)
at software.amazon.awssdk.utils.cache.CachedSupplier.get(CachedSupplier.java:90)
at software.amazon.awssdk.services.sts.auth.StsCredentialsProvider.resolveCredentials(StsCredentialsProvider.java:78)
at software.amazon.awssdk.services.sts.auth.StsAssumeRoleCredentialsProvider.resolveCredentials(StsAssumeRoleCredentialsProvider.java:42)
at software.amazon.awssdk.services.sts.internal.StsProfileCredentialsProviderFactory$StsProfileCredentialsProvider.resolveCredentials(StsProfileCredentialsProviderFactory.java:93)
at software.amazon.awssdk.awscore.internal.client.handler.AwsClientHandlerUtils.createExecutionContext(AwsClientHandlerUtils.java:54)
at software.amazon.awssdk.awscore.client.handler.AwsSyncClientHandler.createExecutionContext(AwsSyncClientHandler.java:65)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler.execute(BaseSyncClientHandler.java:62)
at software.amazon.awssdk.core.client.handler.SdkSyncClientHandler.execute(SdkSyncClientHandler.java:44)
at software.amazon.awssdk.awscore.client.handler.AwsSyncClientHandler.execute(AwsSyncClientHandler.java:53)
at software.amazon.awssdk.services.sts.DefaultStsClient.assumeRole(DefaultStsClient.java:239)
at software.amazon.awssdk.services.sts.auth.StsAssumeRoleCredentialsProvider.getUpdatedCredentials(StsAssumeRoleCredentialsProvider.java:68)
at software.amazon.awssdk.services.sts.auth.StsCredentialsProvider.updateSessionCredentials(StsCredentialsProvider.java:68)
at software.amazon.awssdk.utils.cache.CachedSupplier.refreshCache(CachedSupplier.java:133)
at software.amazon.awssdk.utils.cache.CachedSupplier.get(CachedSupplier.java:90)
at software.amazon.awssdk.services.sts.auth.StsCredentialsProvider.resolveCredentials(StsCredentialsProvider.java:78)
at software.amazon.awssdk.services.sts.auth.StsAssumeRoleCredentialsProvider.resolveCredentials(StsAssumeRoleCredentialsProvider.java:42)
at software.amazon.awssdk.services.sts.internal.StsProfileCredentialsProviderFactory$StsProfileCredentialsProvider.resolveCredentials(StsProfileCredentialsProviderFactory.java:93)
at software.amazon.awssdk.auth.credentials.ProfileCredentialsProvider.resolveCredentials(ProfileCredentialsProvider.java:110)
at software.amazon.awssdk.awscore.internal.client.handler.AwsClientHandlerUtils.createExecutionContext(AwsClientHandlerUtils.java:54)
at software.amazon.awssdk.awscore.client.handler.AwsSyncClientHandler.createExecutionContext(AwsSyncClientHandler.java:65)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler.execute(BaseSyncClientHandler.java:62)
at software.amazon.awssdk.core.client.handler.SdkSyncClientHandler.execute(SdkSyncClientHandler.java:44)
at software.amazon.awssdk.awscore.client.handler.AwsSyncClientHandler.execute(AwsSyncClientHandler.java:53)
at software.amazon.awssdk.services.lambda.DefaultLambdaClient.invoke(DefaultLambdaClient.java:1078)
at com.mytest.ITLambda.tes(ITLambda.java:58)
Caused by: java.net.UnknownHostException: sts.amazonaws.com
at java.net.InetAddress.getAllByName0(InetAddress.java:1280)
at java.net.InetAddress.getAllByName(InetAddress.java:1192)
at java.net.InetAddress.getAllByName(InetAddress.java:1126)
at org.apache.http.impl.conn.SystemDefaultDnsResolver.resolve(SystemDefaultDnsResolver.java:45)
at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:112)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:373)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at software.amazon.awssdk.http.apache.internal.conn.ClientConnectionManagerFactory$Handler.invoke(ClientConnectionManagerFactory.java:80)
at com.sun.proxy.$Proxy0.connect(Unknown Source)
at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:381)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:237)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
at software.amazon.awssdk.http.apache.internal.impl.ApacheSdkHttpClient.execute(ApacheSdkHttpClient.java:72)
at software.amazon.awssdk.http.apache.ApacheHttpClient.execute(ApacheHttpClient.java:200)
at software.amazon.awssdk.http.apache.ApacheHttpClient.access$400(ApacheHttpClient.java:92)
at software.amazon.awssdk.http.apache.ApacheHttpClient$1.call(ApacheHttpClient.java:178)
at software.amazon.awssdk.http.apache.ApacheHttpClient$1.call(ApacheHttpClient.java:175)
at software.amazon.awssdk.core.internal.http.pipeline.stages.MakeHttpRequestStage.executeHttpRequest(MakeHttpRequestStage.java:58)
at software.amazon.awssdk.core.internal.http.pipeline.stages.MakeHttpRequestStage.execute(MakeHttpRequestStage.java:50)
at software.amazon.awssdk.core.internal.http.pipeline.stages.MakeHttpRequestStage.execute(MakeHttpRequestStage.java:34)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:205)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:205)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:205)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:205)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:205)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage$RetryExecutor.doExecute(RetryableStage.java:139)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage$RetryExecutor.execute(RetryableStage.java:109)
... 57 more
`

## Possible Solution
Pass proxy configuration to Sts client.

* AWS Java SDK version used: 2.0.0-preview-12
* JDK version used:1.8.0_171
* Operating System and version: MacOS 10.13.6

Inizia con il flusso del builder di LambdaClient e analizza SdkDefaultClientBuilder quando crea un DefaultStsClientBuilder per il provider delle credenziali. Riproduci la configurazione di proxyConfiguration in relazione alla UnknownHostException segnalata, quindi verifica che il client STS utilizzi la stessa configurazione del proxy e che la richiesta Lambda vada a buon fine.

Scritto dal modello di indicizzazione a partire dal testo della issue.