[DPTP-4326] Updated branches references from "master" to "main"

[hector-vido]

Various references of master branch was renamed to main, this include:

• The minimum tests possible;
• References to openshift/release@master and;
• Default branch names used by some tools.

[openshift-ci]

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[Prucek]

This change needs to be announced to the public and it should be merged right after you rename the branches on o/release and o/ci-tools. I would even announce it beforehand (on XX of March we will rename branches, expect outage for X hours)

[DennisPeriquet]

Our team (CRT) is working to get openshift repos renamed from 'master' to 'main' (working with repo owners who have a better understanding of the consequences of the rename that we do) but I don't know who is planning to do the openshift/release default branch rename.

We think that the o/release repo will be one of the last (if not the very last) repo to rename. As I expect the effects to be broad (though I admit I don't really know how broad), I agree with @Prucek that we will, at the very least, need to announce it with sufficient notice and have some kind of revert/backout/mitigation plan if things go sideways.

[hector-vido]

/hold Needs to synchronize with openshift/release

[openshift-ci]

@hector-vido: 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/breaking-changes	f7f0f58	link	false	/test breaking-changes
ci/prow/integration	f7f0f58	link	true	/test integration
ci/prow/images	f7f0f58	link	true	/test images

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[jmguzik]

I think this PR should be the focus first.
I also think it is not as straightforward as it looks like in this PR.

Whenever "master" is missing in code, it should not be replaced with "main", rather "main" should be added as an option to treat "main" and "master" equally. It is the only path towards smooth transition.

[jmguzik]

This as an example, main should be equal option in the code, not just replacement