Add metrics for in-memory cache

[akashsinghal]

What would you like to be added?

There are 4 in memory caches each using a different implementation. Instrumenting cache metrics for each will add unnecessary overhead. We should wait for all in memory caches to be unified and then add instrumentation on the unified instrument.

Anything else you would like to add?

No response

Are you willing to submit PRs to contribute to this feature?

• [X] Yes, I am willing to implement it.