feat(chunks): support custom MaxIdleConns and MaxIdleConnsPerHost in AWS s3 storage client

[paulojmdias]

What this PR does / why we need it:

Currently, the S3 client used by chunks has the MaxIdleConns and MaxIdleConnsPerHost hardcoded with 200 values. This PR allows both values to be configurable from the client side but keeps the previous hardcoded values as default values.

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.

[mveitas]

@paulojmdias Was there a specific bottleneck or issue with the S3 client this fixes?

[paulojmdias]

@paulojmdias Was there a specific bottleneck or issue with the S3 client this fixes?

Technically no, but we face these hardcoded values in the code during our performance tests. I take the opportunity to make it configurable using the same hardcoded values as default to avoid creating any unexpected change.

[JStickler]

[docs team] Configuration docs updates LGTM.

Someone from the engineering team will have to approve the Go changes.