Exposes prometheus scrape endpoint at /v0/metrics. Runtime overhead is very minimal as we're simply updating a few atomic counters on each call.

Motivation

Currently difficult to see if performance blips in production are due to database slow downs, lock contentions, thread pool queue, or other parts of the code. Having detailed counters allows for easy investigations.

Change Summary

Add metrics module in addon. Metric counters use Atomic numbers and should have very minimal runtime overhead.

Merge Checklist

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Additional Context

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PR-Codex overview

This PR updates the codebase to introduce a new metrics module, adds Counters functionality for tracking store actions, and refactors store definitions.

Detailed summary

• Added metrics module and Counters functionality for tracking store actions.
• Refactored store definitions to include debug names.
• Updated references to statsd with metrics.
• Added rsCountersString function.
• Implemented store action tracking and printing functionality.

The following files were skipped due to too many changes: apps/hubble/src/addon/src/metrics/counters.rs, apps/hubble/src/addon/src/store/store.rs

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