Support single GlanceAPI StatefulSet with regular backends

[fmount]

Starting with RHOSO 19, Nova and Cinder will adopt Glance's new location API,
eliminating the need for default splitting.
This change enables single GlanceAPI deployments with supported backends
(S3, Ceph, Cinder, Swift) for both greenfield and existing environments.

This enables a single Glance StatefulSet deployment with several benefits:

• Reduces PVC resource requirements (e.g., halving staging area storage)
• Simplify deployment topologies and use cases
• Maintains split model for upgrade compatibility

Note: Existing split deployments cannot automatically migrate to single layout.
Manual migration procedures will be documented separately.

Jira: https://issues.redhat.com/browse/OSPRH-17562

[openshift-ci]

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[openshift-merge-robot]

PR needs rebase.

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[openshift-ci]

@fmount: 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/glance-operator-build-kuttl	b6ccb30	link	true	/test glance-operator-build-kuttl
ci/prow/functional	b6ccb30	link	true	/test functional
ci/prow/precommit-check	b6ccb30	link	true	/test precommit-check
ci/prow/glance-operator-build-deploy-tempest	b6ccb30	link	true	/test glance-operator-build-deploy-tempest

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