Adding proxy support for AWS components working with Web Identity Tokens

I try to use Camel AWS S3 with Web Identity Token on Quarkus 2.0.2-Final. I also included AWS STS in the classpath. For local development I need to work with a proxy.

It seems that the proxy settings are taken into account for S3, but are not working for the STS connectivity. The Quarkus start-up finally crashes with a timeout exception:
````
Unable to execute HTTP request: Connect to sts.eu-central-1.amazonaws.com:443 [sts.eu-central-1.amazonaws.com/54.239.54.197] failed: connect timed out
````

I used the following setup:

Route:
````java
from(aws2S3("{{bucketName}}"))
.log("body received: ${body}");
````

application.properties
````ini
# S3 Component
bucketName=my-bucket
camel.component.aws2-s3.region=eu-central-1
camel.component.aws2-s3.useDefaultCredentialsProvider=true
camel.component.aws2-s3.deleteAfterRead=false
camel.component.aws2-s3.prefix=file/path/
%dev.camel.component.aws2-s3.proxyHost=localhost
%dev.camel.component.aws2-s3.proxyPort=3100
%dev.camel.component.aws2-s3.proxyProtocol=http
````

It would be nice if the proxy support could be added (to STS?) for this use case.

Start with the AWS S3 component proxy settings and the Web Identity Token path described in the issue, then reproduce the Quarkus setup using the provided route and application.properties. Trace the STS connectivity used during startup; done means STS requests honor the configured localhost:3100 HTTP proxy and the application starts successfully.

Written by the indexing model from the issue text.