Drop the tracker.

[mattmoor]

Changes

Tekton's use of the tracker is redundant with the informer events it already has configured, and the tracker lease the pipeline run controller is using is probably too small to actually be effective for long-running pipelines.

The tracker is built around the premise that resyncs happen to "refresh" things, and so to be safe the tracker lease should be a multiple of the resync period. The pipeline controller is currently hardcoding 30m, but the default resync period is 10h, so anything taking longer than 30m via the tracker will actually drop events. The controller also seems to track a TaskRun with the name of the PipelineRun, which also feels wrong... 🤔

Fortunately, I believe that both usages of the tracker are wholly redundant with informer events on owned resources anyhow, so this change should just remove unneeded complexity.

For additional background, the purpose of the tracked isn't to track owned resources, but rather to track resources referenced via corev1.ObjectReference (or equivalent). We use this in Knative to track changes to Addressable resources that some resource might be delivering events to (e.g. maybe the address changed, or it is no longer Ready).

/kind cleanup

Submitter Checklist

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

• Docs included if any changes are user facing
• Tests included if any functionality added or changed
• Follows the commit message standard
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  functionality, content, code)
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Release Notes

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cc @dlorenc @imjasonh @vdemeester @afrittoli

[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/reconciler/pipelinerun/pipelinerun.go	83.1%	83.4%	0.3
pkg/reconciler/taskrun/controller.go	96.4%	96.3%	-0.1
pkg/reconciler/taskrun/taskrun.go	76.9%	77.3%	0.4

[mattmoor]

Rebased this on #4110 which just landed.

[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/reconciler/pipelinerun/pipelinerun.go	83.1%	83.4%	0.3
pkg/reconciler/taskrun/controller.go	96.4%	96.3%	-0.1
pkg/reconciler/taskrun/taskrun.go	76.9%	77.3%	0.4

[mattmoor]

/test check-pr-has-kind-label

[mattmoor]

/test check-pr-has-kind-label

[vdemeester]

Seems good to me 😉

[tekton-robot]

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[afrittoli]

Thanks!
Going back all the way to #757, this is the first reference of the tracker that I see, but it was in a different place in the code, and it does not seem to be applicable anymore - today a Pipeline is not marked as done until all associated TaskRun have finished execution in some way.

/lgtm