[OpenShift] Add triggers defaults in CR instead of transformers

[savitaashture]

Changes

Triggers now support config-default-triggers configmap as part of this PR tektoncd/triggers#1182.
PR introduced new attribute trigger in TektonConfig so that user can change the value of service account using CR itself.

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Release Notes

[tekton-robot]

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

File	Old Coverage	New Coverage	Delta
pkg/reconciler/kubernetes/tektonconfig/trigger/trigger.go	69.4%	68.0%	-1.4

[sm43]

/lgtm

[tekton-robot]

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

File	Old Coverage	New Coverage	Delta
pkg/reconciler/kubernetes/tektonconfig/trigger/trigger.go	69.4%	68.0%	-1.4

[tekton-robot]

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

File	Old Coverage	New Coverage	Delta
pkg/reconciler/kubernetes/tektonconfig/trigger/trigger.go	69.4%	72.0%	2.6

[tekton-robot]

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

File	Old Coverage	New Coverage	Delta
pkg/reconciler/kubernetes/tektonconfig/trigger/trigger.go	69.4%	72.0%	2.6

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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[sm43]

/lgtm
/meow

[tekton-robot]

@sm43:

Details

In response to this:

/lgtm
/meow

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