Add FF option disable_process_memory_cache

Related issue: #2509 (closed)

Dependent Upstream MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/111139

What does this MR do and why?

Add feature flag optional cache to disable process memory cache in staging env.

How to check

0. Set ENV DISABLE_FF_PROCESS_MEMORY_CACHE with true or 1
1. Open 2 Rails consoles
2. Check the value of a feature flag on each console: Feature.enabled?(:qa_enforce_locale_to_en)
3. Enable / disable the feature flag in the one console: Feature.enable(:qa_enforce_locale_to_en)
4. Check the value again on the each console (Both terminals return the latest value)