Draft: Inject metrics support into Rails.cache

What does this MR do and why?

Contributes to #413819

Problem

Gitlab::Cache::Client interface is complex to setup. It's not convenient to use it.

Solution

Provide labels for metrics via Rails cache option parameter. It's compatible with 'ActiveSupport::Cache::Store' interface and easy to introduce for existing cache calls.

Roadmap

Step	Description
!122340 (merged)	Initial refactoring to support labels per call
!122341 (merged)	Minor refactoring to set default feature category
!122342 👈	Extend Rails.cache with labels support

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.