Upgrade without killing the CRDs

[vdemeester]

We should make sure we are not deleting / re-creating the tektoncd CRD (PipelineRun, …) if not necessary.
As of today, either we always delete/re-create them or there is some cases where we do…

Doing it is a problem as it will also remove any objects along the way and if any of those objects are in stuck in terminating mode, the whole upgrade process fails and gets stuck.

[jkhelil]

Upgrade implementation is done without CRD deletion, We have seen few cases (customers, and internal cases) where we needed to delete CRDs to start from afresh install, this is mostly due to to one issue related to tekton-pipelines-webhook not being available and preventing upgrade, may be even breaking the process
I beleive that this is adressed by this PR #2630, which is a trial to prevent dedalock during the upgrade process