RHOAIENG-30439: tekton: add PipelineRun definition for minimal CPU Python 3.12 UBI9 runtime (#1497)

* RHOAIENG-30439: tekton: add PipelineRun definition for minimal CPU Python 3.12 UBI9 runtime

* Start by copying the existing -push pipeline.

* Ensure the pipeline pushes to a different image tag and does not overwrite the -push pipeline's image tags.
* Add the pipelinesascode.tekton.dev/cancel-in-progress: "true" annotation.
* Consider adding the pipelinesascode.tekton.dev/on-comment: "^/build" annotation if on-comment builds are desired.
* Use the image-expires-after parameter (e.g., set to 3 days).
* Remove the Slack notification task.
* Incorporate annotations/labels from the auto-generated PR pipeline.

rhoai-ide-konflux#33

* only build PRs in the `opendatahub-io/notebooks` repository

* add timeout, why not

* fix arm64 platform name

* remove additional tags as to not overwrite -push builds

* actually, rabbit may have been right, it's good to define a default ;p

Author: jiridanek