Fix: Expose OpenTelemetry Collector Metrics Endpoint on Port 8888

[alexkroman]

This PR updates the OpenTelemetry Collector configuration to explicitly expose the metrics endpoint on port 8888. Previously, the metrics endpoint was not accessible due to missing configuration settings.

Changes

• Updated otelcol-config.yaml to ensure the metrics endpoint is enabled.
• Verified the configuration aligns with OpenTelemetry's best practices.
• Confirmed that the metrics are now accessible via http://localhost:8888/metrics.

Merge Requirements

For new features contributions, please make sure you have completed the following
essential items:

• CHANGELOG.md updated to document new feature additions
• Appropriate documentation updates in the docs
• Appropriate Helm chart updates in the helm-charts

Maintainers will not merge until the above have been completed. If you're unsure
which docs need to be changed ping the
@open-telemetry/demo-approvers.

[linux-foundation-easycla]

• ✅login: alexkroman / (8d401c6)

The committers listed above are authorized under a signed CLA.

[whuanle]

This issue does not appear to be resolved and a new error has appeared.

[alexkroman]

I'm attaching the screenshot of the error I get when the patch is removed and the successful message I get when it is applied. I haven't been able to reproduce the "server misbehaving" message you're seeing.

[whuanle]

Maybe I can retest it after the code is merged.
I am currently using version v1.5.1.