feat: add KongUpstreamPolicy controller

[czeslavo]

What this PR does / why we need it:

Adds KongUpstreamPolicy controller along with a CLI flag allowing disabling it. Extends stores (prod/fake) to handle the new type. Exposes GetKongUpstreamPolicy from store.Store that will be needed in Parser.

It also moves CacheStores implementation from store.go to a separate cache_stores.go file for better segregation.

Which issue this PR fixes:

Closes #4930.

[codecov]

Codecov Report

Attention: 101 lines in your changes are missing coverage. Please review.

Comparison is base (0a4845a) 77.7% compared to head (26c500c) 77.5%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #4969     +/-   ##
=======================================
- Coverage   77.7%   77.5%   -0.3%     
=======================================
  Files        166     167      +1     
  Lines      18624   18708     +84     
=======================================
+ Hits       14476   14500     +24     
- Misses      3315    3368     +53     
- Partials     833     840      +7     

Files	Coverage Δ
internal/manager/config.go	93.1% <100.0%> (+<0.1%)	⬆️
internal/manager/controllerdef.go	99.4% <100.0%> (+<0.1%)	⬆️
internal/store/fake_store.go	39.2% <57.1%> (+0.5%)	⬆️
internal/store/store.go	70.3% <70.0%> (-0.4%)	⬇️
...trollers/configuration/zz_generated_controllers.go	47.1% <20.4%> (-1.2%)	⬇️
internal/store/cache_stores.go	72.4% <72.4%> (ø)

... and 6 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[pmalek]

👍