feat(kuma-cp): support Retry policy for Gateways

[jpeach]

Summary

Add Retry support to Gateway routes. This takes a different approach
from mesh, but populating the retry policy on the routing route action.
Since Retry is a connection policy that matches a sources and destination,
the routing step is the best place to attach the policy since at that
point we know both the source and the destination services. The only
complication is when we are forwarding to a weighted cluster composed
of multiple services, where the selected policy may not be especially
obvious.

Full changelog

N/A

Issues resolved

Fix #3319.

Documentation

N/A

Testing

• Unit tests
• E2E tests
• Manual testing on Universal
• Manual testing on Kubernetes

Backwards compatibility

• Update UPGRADE.md with any steps users will need to take
  when upgrading.
• Add backport-to-stable label if the code is backwards compatible. Otherwise, list breaking changes.

[codecov-commenter]

Codecov Report

Merging #3402 (a5f9d08) into master (e36d451) will increase coverage by 0.08%.
The diff coverage is 60.94%.

@@            Coverage Diff             @@
##           master    #3402      +/-   ##
==========================================
+ Coverage   52.18%   52.26%   +0.08%     
==========================================
  Files         940      941       +1     
  Lines       54677    54837     +160     
==========================================
+ Hits        28532    28663     +131     
- Misses      23927    23946      +19     
- Partials     2218     2228      +10     

Impacted Files	Coverage Δ
pkg/plugins/runtime/gateway/route/configurers.go	73.28% <46.05%> (-9.59%)	⬇️
pkg/plugins/runtime/gateway/match/policy.go	85.71% <66.66%> (-14.29%)	⬇️
...g/plugins/runtime/gateway/route_table_generator.go	81.19% <66.66%> (-18.81%)	⬇️
pkg/plugins/runtime/gateway/cluster_generator.go	88.28% <100.00%> (-0.41%)	⬇️
pkg/plugins/runtime/gateway/generator.go	78.62% <100.00%> (+0.45%)	⬆️
pkg/plugins/runtime/gateway/route/util.go	100.00% <100.00%> (ø)
pkg/xds/envoy/listeners/v3/retry_configurer.go	83.05% <100.00%> (ø)
api/observability/v1/mads.pb.go	35.56% <0.00%> (+1.03%)	⬆️
pkg/mads/v1/client/client.go	43.75% <0.00%> (+2.50%)	⬆️
... and 5 more

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