Support manual cache eviction

[hwillson]

Broken out from #2331. We'll use this issue to track cache eviction feature work.

Side note: we need to look into how much of this is already possible with apolloStore.remove().

[martinbonnin]

Turns out apolloStore.remove(CacheKey) is doing the job. What we're missing is a way to handle dangling references after an entity has been removed. See apollographql/apollo-kotlin-normalized-cache-incubating#85 for a follow up.