contrib/aws: add go.mod to isolate contrib

[darccio]

What does this PR do?

Isolates contrib/aws as an independent module, and adds the support for running contrib modules' tests in CI.

This will be done for each contrib, and this is a first PR to validate the approach. Next PRs will consist of multiple contribs.

Motivation

Security scanners yield false positives, informing vulnerable versions that are present in the go.mod but not compiled into the final binary.

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• 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.

For Datadog employees:

• If this PR touches code that handles credentials of any kind, such as Datadog API keys, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2023-11-21 13:52:58

Comparing candidate commit 1a03b23 in PR branch dario.castane/AIT-8717/isolate-contribs with baseline commit 0fa8d63 in branch v2-dev.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 39 metrics, 2 unstable metrics.

[darccio]

CI is working: