gatewayapi: add support for route rule filters

[aryan9600]

Add support for Filters in the HTTPRoute API. We reuse most of the existing fields used for Istio to construct the appopriate filter. A new API .spec.service.mirror is added to allow for request mirroring. The .spec.service.rewrite API has been changed to a custom HTTPRewrite API instead of importing it from Istio, to allow covering all features that Gateway API provides.
Support for the RequestRedirect Filter has been left out on purpose, since it's not possible to specify it if the same rule also specifies .backendRefs (which Flagger does).

Fixes #1488

[stefanprodan]

Mirroring is a property of the analysis, so I would expect for Flagger to configure Gateway API mirroring automatically, from primary to canary based on .spec.analysis.mirror.

[aryan9600]

i think we should allow for mirroring using both service and analysis. .spec.analysis.mirror would enable request mirroring to the Canary deployment, while .spec.service.mirror would mirror the request to the specified backend.

since adding support for .spec.analysis.mirror means adding support for the B/G mirror deployment strategy and would probably require changes in other places like the scheduler, i suggest we tackle that in another PR.

[stefanprodan]

LGTM

Thanks @aryan9600

[codecov-commenter]

Codecov Report

Patch coverage: 27.02% and project coverage change: -0.32% ⚠️

Comparison is base (aaafdca) 55.28% compared to head (c0e2096) 54.96%.
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1512      +/-   ##
==========================================
- Coverage   55.28%   54.96%   -0.32%     
==========================================
  Files          85       85              
  Lines       10233    10325      +92     
==========================================
+ Hits         5657     5675      +18     
- Misses       3917     3988      +71     
- Partials      659      662       +3     

Files Changed	Coverage Δ
pkg/controller/scheduler.go	45.30% <0.00%> (ø)
pkg/controller/scheduler_hooks.go	13.79% <0.00%> (ø)
pkg/router/gateway_api_v1beta1.go	48.36% <7.50%> (-7.42%)	⬇️
pkg/canary/spec.go	84.00% <100.00%> (ø)
pkg/canary/status.go	47.17% <100.00%> (ø)
pkg/controller/webhook.go	69.41% <100.00%> (+5.02%)	⬆️
pkg/router/istio.go	77.57% <100.00%> (ø)

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