fix: enhance release docs and pipeline definitions

[anithapriyanatarajan]

Changes

This pull request updates the Tekton CI/CD configuration and documentation to support official releases for the Tekton Pruner project. The changes primarily rename and tailor pipeline resources for Pruner, add comprehensive release instructions, and clarify resource management for nightly builds.

Key changes include:

• Renamed pipeline and tasks from generic or "pipeline" names to Pruner-specific names in tekton/release-pipeline.yaml and tekton/publish.yaml
• Added a new tekton/README.md explaining the CI/CD setup and how to use Tekton Pipelines for Pruner.
• Introduced a detailed tekton/release-cheat-sheet.md with step-by-step instructions for performing official Pruner releases.
• Updated the nightly build GitHub Actions workflow to use the Pruner-specific pipeline and clarified why certain RBAC steps are kept separate
• Removed account.yaml from tekton/kustomization.yaml to avoid affecting the main release pipeline, ensuring it is only applied where needed.

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• Has Docs if any changes are user facing, including updates to minimum requirements e.g. Kubernetes version bumps
• Has Tests included if any functionality added or changed
• pre-commit Passed
• Follows the commit message standard
• Meets the Tekton contributor standards (including functionality, content, code)
• Has a kind label. You can add one by adding a comment on this PR that contains /kind <type>. Valid types are bug, cleanup, design, documentation, feature, flake, misc, question, tep
• Release notes block below has been updated with any user facing changes (API changes, bug fixes, changes requiring upgrade notices or deprecation warnings). See some examples of good release notes.
• Release notes contains the string "action required" if the change requires additional action from users switching to the new release

Release Notes

NONE

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This pull-request has been approved by: savitaashture

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[infernus01]

/lgtm