gha: add sync workflow

[dtrifiro]

Runs nightly and creates (or updates) a PR pulling the latest changes from upstream into the main branch

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[dtrifiro]

Example PR here dtrifiro#6

[z103cb]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dtrifiro, z103cb

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[openshift-ci]

New changes are detected. LGTM label has been removed.

[openshift-ci]

@dtrifiro: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/images	4ad6609	link	true	/test images
ci/prow/pr-image-mirror	4ad6609	link	true	/test pr-image-mirror

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