feat: Add filter function to reflector::Store

[JPaja]

Motivation

To get list of items that match predicate from store requires using 'state' function first.
This clones all elements instead of just filtered ones.

store.state().into_iter().filter(predicate).collect::<Vec<_>>()

Solution

Add function called 'filter' in store that first filters elements and than clones.

store.filter(predicate)

[clux]

Hey there, thanks for this.

I think the rational to avoid cloning here makes sense, but it brings up a point we have talked about before; that maybe we should expose an iterator state() equivalent instead? We have previously received PRs wanting to extend Store and it feels like we end up re-implementing all the map accessors.

See e.g. #1634 (comment) WDYT? Is an Iterator return type something that would be suitable here?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.0%. Comparing base (6a980c6) to head (031bd3e).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1681     +/-   ##
=======================================
+ Coverage   75.9%   76.0%   +0.1%     
=======================================
  Files         84      84             
  Lines       7611    7640     +29     
=======================================
+ Hits        5771    5800     +29     
  Misses      1840    1840             

Files with missing lines	Coverage Δ
kube-runtime/src/reflector/store.rs	97.5% <100.0%> (+0.6%)	⬆️

[JPaja]

hi @clux, Yeah any solution that does not require cloning everything would work, Regarding iterator solution I'm just worried that RwLock read reference could cause problems in terms of locking out potential writes, because users are responsible of sanely dropping it.

Maybe implementing Read/AsyncRead on Cache would solve issue here, allowing AsyncReadExt to handle all possible functions