Consuming repos on stable branches are getting broken by changes to knative/actions

All our repos are reusing actions with by using `@main` version. The actions are evolving, which is normal, but that breaks those support branches.

We need to start creating tags or at least branches on [knative/actions](https://github.com/knative/actions/).

When incompatibility occurs we could switch failing repo to older, passing action ie.: `@release-1.7`. This approach has a disadvantage. People may be confused why their stable branch is broken...

We could also consider to proactively switch actions to branch of `knative/actions` at release day. This adds churn, but it ensures we can always release if needed.

Start by inventorying how consuming repositories reference knative/actions and review the versioning options described in this issue: tags, release branches, or proactive updates on release day. Compare how each option protects stable branches from incompatible changes. Done means an agreed versioning policy is implemented so stable branches do not depend on moving @main.

Written by the indexing model from the issue text.