Make downstream otlp host configurable

[jorbaum]

Make downstream otlp host configurable. Similar to https://github.com/cloudfoundry/loggregator-agent-release/pull/708/changes , but for otlp egress, not for loggregator envelope ingress.

We need this as in kind-deployment otel-collector and forwarder agent do not run on the same machine (see cloudfoundry/kind-deployment#493 ).

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Testing performed?

• Unit tests
• Integration tests
• Acceptance tests

Checklist:

• This PR is being made against the main branch, or relevant version branch
• I have made corresponding changes to the documentation
• I have added testing for my changes

If you have any questions, or want to get attention for a PR or issue please reach out on the #logging-and-metrics channel in the cloudfoundry slack

[jorbaum]

Tested by deploying this in cf on kind via cloudfoundry/kind-deployment#493 and checking via an external otel-collector-outside-kind that metrics are being forwarded.

I think this is a small enough change so we do not need to verify this again on an actual foundation. However, I could test it there again as well if required.