Add telemetry catalogs and weaver gen for metadata.yaml used by mdatagen

[CodeMonkeyF5]

Proposed changes

These changes introduce a single source-of-truth for Agent V3 OTel metrics by creating a telemetry catalog that conforms to Weaver standards. Additionally, it automatically generates the metadata.yaml files used by the mdatagen tool to produce all needed outputs for the collectors (nginxoss, nginxplus).

Checklist

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• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13

[github-actions]

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[CodeMonkeyF5]

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[CodeMonkeyF5]

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