feat(aws_cloudwatch_logs sink): implement log_group_class config for CloudWatch Logs sink

[cahartma]

Summary

Resolves issue #24320 by adding the option to set the log class when creating a log group using the CloudWatch Logs sink. Simple config and client update to pass along a string value when creating the log group.

Vector configuration

# Cloudwatch Logs Sink
[sinks.output_my_cw]
type = "aws_cloudwatch_logs"
region = "us-east-2"
group_name = "my-new-group"
log_group_class = "infrequent_access"
...

How did you test this PR?

Tested by sending logs to CW and verifying the log_group_class of the newly created group.

Change Type

• [ ] Bug fix
• [ ] New feature
• [x] Enhancement
• [ ] Non-functional (chore, refactoring, docs)
• [ ] Performance

Is this a breaking change?

• [ ] Yes
• [x] No

Does this PR include user facing changes?

• [x] Yes. Please add a changelog fragment based on our guidelines.
• [ ] No. A maintainer will apply the no-changelog label to this PR.

References

• Closes: #24320

Notes

• Please read our Vector contributor resources.
• Do not hesitate to use @vectordotdev/vector to reach out to us regarding this PR.
• Some CI checks run only after we manually approve them.
  • We recommend adding a pre-push hook, please see this template.
  • Alternatively, we recommend running the following locally before pushing to the remote branch:
    • make fmt
    • make check-clippy (if there are failures it's possible some of them can be fixed with make clippy-fix)
    • make test
• After a review is requested, please avoid force pushes to help us review incrementally.
  • Feel free to push as many commits as you want. They will be squashed into one before merging.
  • For example, you can run git merge origin master and git push.
• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please run make build-licenses to regenerate the license inventory and commit the changes (if any). More details here.