Add stage override variable to shiftstack role

[tusharjadhav3302]

The shiftstack role invokes ocp_testing.yaml with a testconfig that bundles all stages (install + test) in a single ansible-navigator call. The upcoming phased pipeline needs to run install stages in one Zuul job and test stages in another, using the same testconfig file.

Add cifmw_shiftstack_stages_override (default: []) that appends --extra-vars to the ansible-navigator command when non-empty, overriding the stages list from the testconfig. This avoids creating per-phase testconfig files in shiftstack-qa and keeps the monolithic job unchanged (empty list = no override = all stages run as before).

Related-Issue: OSPRH-33128

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[openshift-ci]

Hi @tusharjadhav3302. Thanks for your PR.

I'm waiting for a openstack-k8s-operators member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

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https://gateway-cloud-softwarefactory.apps.ocp.cloud.ci.centos.org/zuul/t/rdoproject.org/buildset/88db85dc71f04addbfafd2d0db930519

✔️ openstack-k8s-operators-content-provider SUCCESS in 2h 42m 01s
✔️ podified-multinode-edpm-deployment-crc SUCCESS in 1h 39m 34s
✔️ cifmw-crc-podified-edpm-baremetal SUCCESS in 1h 49m 32s
✔️ cifmw-crc-podified-edpm-baremetal-minor-update SUCCESS in 2h 21m 55s
✔️ cifmw-pod-zuul-files SUCCESS in 5m 43s
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✔️ noop SUCCESS in 0s
✔️ cifmw-pod-ansible-test SUCCESS in 9m 06s
✔️ cifmw-pod-pre-commit SUCCESS in 9m 54s
✔️ cifmw-molecule-shiftstack SUCCESS in 20m 32s