Introduce custom sync-downstream GHA, this can handle known conflicts

[atheo89]

Related to: https://issues.redhat.com/browse/RHOAIENG-15392

Description

This GitHub Action aims to sync the downstream branch with the corresponding upstream, resolve known conflicts, and generates a pull request.

How has been tested

Created a simulated org for dev and test purposes:
Some gh runs: https://github.com/Org-Test-Template/notebooks/actions/workflows/sync-downstream.yaml
Example PRs: https://github.com/Org-Test-Template/notebooks/pulls

[openshift-ci]

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[openshift-ci]

@jiridanek: Overrode contexts on behalf of jiridanek: ci/prow/images

In response to this:

/override ci/prow/images
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[jiridanek]

/lgtm
this looks like the tried and true strategy from odh-io/kubeflow; it's just that we won't be able to use the devops sync action and will have to have our custom one, because the devops action can't handle these conflicts; but no matter

[atheo89]

/override ci/prow/images

[openshift-ci]

@atheo89: Overrode contexts on behalf of atheo89: ci/prow/images

In response to this:

/override ci/prow/images

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[atheo89]

/lgtm this looks like the tried and true strategy from odh-io/kubeflow; it's just that we won't be able to use the devops sync action and will have to have our custom one, because the devops action can't handle these conflicts; but no matter

That's true, however, when we onboard onto Konflux, we'll have a better understanding of how to handle this more efficiently. Until then, we'll need to fast track the current procedure to keep things moving forward.

[jiridanek]

/lgtm

[atheo89]

/override ci/prow/images

[openshift-ci]

@atheo89: Overrode contexts on behalf of atheo89: ci/prow/images

In response to this:

/override ci/prow/images

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.