Explore SS Cache

[alexanderbez]

Currently the SS layer has zero explicit caching (the underlying DB itself may of course cache but that is opaque to us).

This issue is to mainly explore if we should add an explicit cache layer to the SS backend. The cache, if it were to exist, would be isolated and local to SS only (i.e. not a KVStore). It would also store bytes, not objects.

This should be explored post initial release as it's not critical.

cc @tac0turtle @testinginprod

[julienrbrt]

SS is gone since #22683