feat: add KEDA HTTPScaledObjects support

[kahirokunn]

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 11.95721% with 1399 lines in your changes missing coverage. Please review.

Project coverage is 37.43%. Comparing base (febc327) to head (69dda9f). Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/apis/http/v1alpha1/zz_generated.deepcopy.go	0.00%	497 Missing :warning:
pkg/apis/http/v1alpha1/httpscalingset_defaults.go	0.00%	95 Missing :warning:
pkg/canary/http_scaled_object_reconciler.go	0.00%	89 Missing :warning:
...d/http/v1alpha1/fake/fake_clusterhttpscalingset.go	0.00%	77 Missing :warning:
.../typed/http/v1alpha1/fake/fake_httpscaledobject.go	0.00%	77 Missing :warning:
...ed/typed/http/v1alpha1/fake/fake_httpscalingset.go	0.00%	77 Missing :warning:
...ped/gatewayapi/v1beta1/fake/fake_referencegrant.go	22.05%	52 Missing and 1 partial :warning:
pkg/apis/flagger/v1beta1/zz_generated.deepcopy.go	3.77%	50 Missing and 1 partial :warning:
...g/apis/gatewayapi/v1beta1/zz_generated.deepcopy.go	41.37%	50 Missing and 1 partial :warning:
...ntset/versioned/typed/http/v1alpha1/http_client.go	0.00%	48 Missing :warning:
... and 30 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1748      +/-   ##
==========================================
- Coverage   39.27%   37.43%   -1.85%     
==========================================
  Files         284      311      +27     
  Lines       22379    23872    +1493     
==========================================
+ Hits         8789     8936     +147     
- Misses      12643    13978    +1335     
- Partials      947      958      +11     

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