contrib/aws/aws-sdk-go-v2/aws: Fix streamName nil pointer panic

[webdestroya]

According to the AWS Kinesis API Docs:

When invoking this API, you must use either the StreamARN or the StreamName parameter, or both. It is recommended that you use the StreamARN input parameter when you invoke this API.

Currently, if requests use only the StreamARN parameter (as recommended by AWS), the streamName function will panic with a nil pointer.

I've updated the function to return the name first (if provided) to keep backwards compatibility. If that is nil, then it uses the resource part of the ARN. If that is nil, it returns empty string instead of panicking.

I added a second method coalesceNameOrArnResource (if you have a better name, let me know) to prevent having the code be copy/pasted for each switch member.

What does this PR do?

• Fixes a nil pointer panic in aws streamName integration

Motivation

• I'd rather my app not explode when publishing records

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

[rarguelloF]

LGTM, Thanks for fixing this issue!