TEP-0114: Custom Tasks Beta - Feature Gates

[jerop]

In TEP-0114: Custom Tasks Beta, we proposed migrating Custom Tasks and Runs to beta.

This issue tracks this feature gates changes - stop guarding of Custom Tasks behind enable-custom-tasks and enable-api-fields feature gates.

• [ ] 1. Change default value of enable-custom-tasks from "false" to "true"
• [ ] 2. Remove enable-custom-tasks
• [ ] 3. Stop guarding Custom Tasks use in Pipelines behind enable-api-fields being set to "alpha"

[JeromeJu]

/assign

[tekton-robot]

Issues go stale after 90d of inactivity. Mark the issue as fresh with /remove-lifecycle stale with a justification. Stale issues rot after an additional 30d of inactivity and eventually close. If this issue is safe to close now please do so with /close with a justification. If this issue should be exempted, mark the issue as frozen with /lifecycle frozen with a justification.

/lifecycle stale

Send feedback to tektoncd/plumbing.

[jerop]

Completed in https://github.com/tektoncd/pipeline/pull/5858