feat: Cerbos Cloud bundle store driver

[charithe]

Introduces a new storage driver that connectes to Cerbos Cloud to
receive optimized policy bundles.

Signed-off-by: Charith Ellawala charith@cerbos.dev

[codecov]

Codecov Report

Merging #1530 (84dc608) into main (df020fb) will decrease coverage by 2.56%.
The diff coverage is 44.72%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1530      +/-   ##
==========================================
- Coverage   53.94%   51.38%   -2.56%     
==========================================
  Files         122       88      -34     
  Lines       13585    10002    -3583     
==========================================
- Hits         7328     5140    -2188     
+ Misses       5634     4416    -1218     
+ Partials      623      446     -177     

Impacted Files	Coverage Δ
internal/namer/namer.go	64.37% <0.00%> (-0.82%)	⬇️
internal/storage/bundle/source_wrappers.go	0.00% <0.00%> (ø)
internal/util/app.go	0.00% <0.00%> (ø)
internal/storage/bundle/store.go	1.61% <1.61%> (ø)
internal/storage/bundle/conf.go	28.57% <28.57%> (ø)
private/verify/verify.go	34.00% <52.63%> (+9.00%)	⬆️
internal/storage/bundle/remote_source.go	57.27% <57.27%> (ø)
internal/storage/bundle/bundle.go	57.51% <57.51%> (ø)
internal/storage/bundle/local_source.go	61.11% <61.11%> (ø)

... and 43 files with indirect coverage changes

[dbuduev]

LGTM 👍🏻
Except for the removal of the bundle protobuf code, it seems the change is purely incremental, which is awesome.