Bump k8s api to v0.27.6 and contour to 1.26.0

[andrew-su]

Changes

• Bump contour to 1.26.0
• Bump k8s API to 0.27.6
• Force kube-openapi to be the same version used by k8s.io/client-go@0.27.6.
  • Letting this update to latest (>= 0.28.0) causes a dependency issue as github.com/google/gnostic had been split out into github.com/google/gnostic-models
• Force code-generator to be v0.27.6.
  • The newer version of k8s.io/code-generator executes generate-internal-groups.sh which we currently do not set the exec flag from the knative.dev/hack module. (To be removed when Update codegen-library.sh to set exec flag on new k8s.io/code-generator scripts knative/hack#335 or Use kube-codegen.sh instead of generate-groups.sh when moving to k8s.io api 0.28+ knative/hack#336 is done)

/kind enhancement

Fixes #960

[codecov]

Codecov Report

Merging #974 (f18b0a0) into main (cf267c1) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #974   +/-   ##
=======================================
  Coverage   93.89%   93.89%           
=======================================
  Files           7        7           
  Lines         802      802           
=======================================
  Hits          753      753           
  Misses         28       28           
  Partials       21       21           

[andrew-su]

/test build-tests

[andrew-su]

/test integration-tests

[dprotaso]

/lgtm
/approve

[dprotaso]

/hold - we should actually bump to the right k8s client-go version - for v1.12 that's 1.27.x

[dprotaso]

Might want to wait for this bump first

#973

[dprotaso]

@andrew-su all the stuff has merged - so you're good to continue

[andrew-su]

Updated.
I had chosen to use the same versions as what we currently have for the other k8s dependencies, however it looks like the codegen still work with:

	k8s.io/code-generator => k8s.io/code-generator v0.27.6
	k8s.io/kube-openapi => k8s.io/kube-openapi v0.0.0-20230501164219-8b0f38b5fd1f

Should I bump it to ^ or leave it for consistency?

[dprotaso]

We can match serving with v0.27x deps. Next release we are targeting k8s min version of 1.26 which means we can use 1.27 libs

https://github.com/knative/serving/blob/6703812f131472daa5b7f17e60dd7f49a06c1ead/go.mod#L28

[andrew-su]

/retest

[dprotaso]

/lgtm
/approve

[knative-prow]

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[dprotaso]

/hold cancel