Add option to AWSConfigs to only use ec2 instance profile role for AWSCredentials

### Describe the feature

Allow specifying which `AWSCredentials` source to use so that we can ensure our application only uses credentials from one source (instance profile).

### Use Case

We are currently using `InstanceProfileAWSCredentials` to make sure we only get credentials from the instance profile. This has the downside that if the instance profile associated with the EC2 instance is changed, then the .NET application will still attempt to retrieve credentials for the old instance profile and fail. The new instance profile is only picked up after the application is restarted.

We want to prevent any other credential source from being used but still automatically refresh the instance profile after a different instance profile is associated with the EC2 instance. (Skip to the last entry (Amazon EC2 instance metadata) in the [Credential and profile resolution](https://docs.aws.amazon.com/sdk-for-net/v3/developer-guide/creds-assign.html))

### Proposed Solution

Add an option to `AWSConfigs` like `AWSProfileOnlyInstanceProfile` so that we can use the default way to get/refresh credentials but still prevent credentials from different sources from accidentally being used.

### Other Information

Error message trying to `s3:PutObject` using `InstanceProfileAWSCredentials` after a different instance profile is associated with the EC2 instance
```
Amazon.Runtime.AmazonClientException: The retrieved credentials have already expired: Now = 07/09/2024 05:37:58, Credentials expiration = 07/09/2024 05:37:55
at Amazon.Runtime.RefreshingAWSCredentials.UpdateToGeneratedCredentials(CredentialsRefreshState state, TimeSpan preemptExpiryTime) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Credentials\RefreshingAWSCredentials.cs:line 185
at Amazon.Runtime.RefreshingAWSCredentials.GetCredentials() in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Credentials\RefreshingAWSCredentials.cs:line 133
at Amazon.Runtime.Internal.CredentialsRetriever.PreInvoke(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\CredentialsRetriever.cs:line 54
at Amazon.Runtime.Internal.CredentialsRetriever.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\CredentialsRetriever.cs:line 72
at Amazon.Runtime.Internal.RetryHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\RetryHandler\RetryHandler.cs:line 91
at Amazon.Runtime.Internal.CallbackHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\CallbackHandler.cs:line 46
at Amazon.Runtime.Internal.CallbackHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\CallbackHandler.cs:line 46
at Amazon.S3.Internal.AmazonS3ExceptionHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Services\S3\Custom\Internal\AmazonS3ExceptionHandler.cs:line 48
at Amazon.Runtime.Internal.ErrorCallbackHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\ErrorCallbackHandler.cs:line 44
at Amazon.Runtime.Internal.MetricsHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\MetricsHandler.cs:line 40
at Amazon.Runtime.Internal.RuntimePipeline.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\RuntimePipeline.cs:line 136
at Amazon.Runtime.AmazonServiceClient.Invoke[TResponse](AmazonWebServiceRequest request, InvokeOptionsBase options) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\AmazonServiceClient.cs:line 203
```

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### AWS .NET SDK and/or Package version used

AWSSDK.Core 3.7.0.17

### Targeted .NET Platform

.NET framework 4.7.2

### Operating System and version

Windows 10

Start with AWSConfigs and the credential-resolution path described in the issue, then compare it with InstanceProfileAWSCredentials. Define how the new option selects only EC2 instance metadata credentials while retaining automatic refresh after an instance-profile change. Done means the selected mode cannot fall back to other credential sources and continues to refresh the active instance profile.

Written by the indexing model from the issue text.