Replace kubebuilder-release-tools action

[sbueringer]

Sooner or later the kubebuilder-release-tools actions will have to either migrate to the community-registry or be deprecated (https://github.com/kubernetes-sigs/kubebuilder-release-tools/issues/60#issuecomment-2236068489).

While thinking about this, I was wondering if we actually need the kubebuilder-release-tools action in Cluster API. Especially considering how much effort it took the last time to get a change implemented in kubebuilder-release-tools and the action correctly published and bumped.

I took a closer look and it looks like we use it only to verify PR titles in the following way:

• to check for icons (while ignoring e.g. WIP): https://github.com/kubernetes-sigs/kubebuilder-release-tools/blob/master/verify/type.go
• to check if there is an issue referenced in the PR title: https://github.com/kubernetes-sigs/kubebuilder-release-tools/blob/master/verify/issue.go

I think we can replace the usage of kubebuilder-release-tools with a small GitHub action that just runs some local code (e.g. bash) to achieve the same goal.

Once implemented, let's make sure we surface this alternative implementation at the kubebuilder-release-tools issue (https://github.com/kubernetes-sigs/kubebuilder-release-tools/issues/60)

[sbueringer]

/help

[k8s-ci-robot]

@sbueringer: This request has been marked as needing help from a contributor.

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[sbueringer]

/triage accepted

[sivchari]

I work on it. /assign

[sbueringer]

One quick comment. Would be nice if it's just one self-contained action YAML. So it's easy to copy / sync to other projects