Add custom InstanceProfileCredentialsProvider with more resilience to throttling

Add our own InstanceProfileCredentialsProvider class which uses the AWS implementation to retrieve credentials from EC2's instance info, but more resilient to overloading.

1. pass in client config with retry logic (HADOOP-15603)
2. use Invoke.retry() to retry
3. log/measure failures
4. maybe use the Async feature of the AWS SDK class, so that credential renewer doesn't block IO.
5. be shared amongst all AWS auth chains which need these credentials.

The singleton we current use for IAM auth doesn't do async, which is good as it ensures that we don't prematurely close it when AWSCredentialProviderList.close() closes its children.