RFC: Add FailureReason field for PipelineRun and TaskRun Status

[JeromeJu]

Changes

This PR adds the new field FailureReason for PipelineRunStatus
and TaskRun status. It aims to provide more granular reasons with
backwards compatibility kept while making changes to the existing error
reasons.

part of #7396

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
• Follows the commit message standard
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• 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

[tekton-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[tekton-robot]

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[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-pipeline-go-coverage-df to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/apis/pipeline/v1/pipelinerun_types.go	89.5%	88.7%	-0.8
pkg/apis/pipeline/v1/taskrun_types.go	81.4%	80.0%	-1.4

[tekton-robot]

@JeromeJu: PR needs rebase.

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