Store Gateway: Inmemory chunks cache

[yeya24]

Is your feature request related to a problem? Please describe.
For scenarios where rules are configured to query Store Gateway, Store Gateway can query the same chunks over and over again.

Existing chunk cache only supports memcached and Redis. Fetching the same data over network could increase the bandwidth usage baseline, which is not ideal

Describe the solution you'd like
Add a new inmemory chunks cache backend so that chunks can be stored inmemory.