CMM cache has no instrumentation

### Problem:

when using, and configuring the SDK, it would be good to understand the performance of the CMM cache, as having the cache to small can hurt performance

### Solution:

We could add open telemetry performance, maybe as an optional feature on the cache (that is what I have done in our application)

Happy to contribute this is its useful, and with some steer form the maintainers

In general is there a policy for instrumentation in thi project?

### Out of scope:

Start by locating the CMM cache implementation and reviewing project guidance on instrumentation. Confirm the maintainers' preferred OpenTelemetry policy and define the scope of optional cache performance measurements; done means an agreed, tested instrumentation approach.

Scritto dal modello di indicizzazione a partire dal testo della issue.