OSSM-3551 Add metadata stub for 3.0

[dgn]

This is really just to get CPaaS builds going. Once we implement proper operator support (or later), we'll need to think about how we manage metadata in the future, as we'll want to maintain separate channels for 2.x and 3.x streams. It also pulls in some newer commits from the 2.4 branch

[openshift-ci]

@dgn: 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/maistra-istio-operator-gencheck-2-4	3a66531	link	true	/test maistra-istio-operator-gencheck-2-4
ci/prow/istio-operator-push-image-2-4	3a66531	link	true	/test istio-operator-push-image-2-4

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[dgn]

cc @aslakknutsen

[dgn]

/retest