[Feature]: Prometheus Metrics Abstraction

[mladjan-gadzic]

Purpose

Implemented feature #30394

Test Plan

Added tests.

Test Result

All metrics test passes.

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
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[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @mladjan-gadzic.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[gemini-code-assist]

Code Review

This pull request introduces a well-designed abstraction layer for metrics, which will make it easier to support different backends like Prometheus and OpenTelemetry in the future. The refactoring of existing metric collection points to use this new abstraction is thorough. I've found one critical issue related to a leaky abstraction that needs to be addressed to ensure backend-agnostic behavior.

[gemini-code-assist]

The method set_to_current_time() is specific to the prometheus-client and is not part of the AbstractGauge interface. Using it breaks the abstraction layer you've introduced, and it will cause a runtime error if a different metrics backend (like the prototype OTEL one) is used.

To fix this and adhere to the abstraction, you should use the set() method from the AbstractGauge interface with the current time. The type: ignore is still necessary due to how labels() is typed in the base class, which is a separate typing issue.

Suggested change

	self.gauge_lora_info.labels(**lora_info_labels).set_to_current_time() # type: ignore[attr-defined]
	self.gauge_lora_info.labels(**lora_info_labels).set(time.time()) # type: ignore[attr-defined]

[bbartels]

A couple follow up clean-up tasks would be good, ideally any publisher of metrics isn't aware of which backend is being exported to, so references to prometheus could be cleaned up in various places (assuming it doesn't break public API surface).

Worth updating docs (if there are any) to reflect these changes so developers are aware of the changes of how to register metrics