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
• Enhancement
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

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

References

• Closes: Support Log Classes for CloudWatch Logs #24320

Notes

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