Recover Conversion Functions from Pipeline Resources for backwards compatibility

[chitrangpatel]

Changes

When we reverted removal of PipelineResources related fields,
we did not recover the conversion functions. As a result, when migrating
Tekton Chains to watch v1 objects, we run into Issue #7105.

This PR recovers the conversion functions so that we can continue to convert PipelineResources related fields. It addresses issue #7105.

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
• 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
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• Release notes contains the string "action required" if the change requires additional action from users switching to the new release

Release Notes

Recover Conversion Functions from Pipeline Resources for backwards compatibility

/kind bug

[chitrangpatel]

/assign @wlynch

[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/v1beta1/pipeline_conversion.go	96.5%	95.3%	-1.2
pkg/apis/pipeline/v1beta1/pipelinerun_conversion.go	96.8%	95.7%	-1.1
pkg/apis/pipeline/v1beta1/task_conversion.go	93.2%	91.9%	-1.3
pkg/apis/pipeline/v1beta1/taskrun_conversion.go	94.1%	93.1%	-0.9

[tekton-robot]

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

File	Old Coverage	New Coverage	Delta
pkg/apis/pipeline/v1beta1/pipeline_conversion.go	96.5%	95.3%	-1.2
pkg/apis/pipeline/v1beta1/pipelinerun_conversion.go	96.8%	95.7%	-1.1
pkg/apis/pipeline/v1beta1/task_conversion.go	93.2%	91.9%	-1.3
pkg/apis/pipeline/v1beta1/taskrun_conversion.go	94.1%	93.1%	-0.9

[Yongxuanzhang]

/lgtm

[wlynch]

/approve

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wlynch

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