Delete next cell irrespective of last deletion

[auniyal61]

Right now when multiple cells gets deleted if any one the cell deletion fails, the control exits with error msg.
This change stores the errors in a list and let next cells deleted.

Closes #OSPRH-10550

[auniyal61]

The jira report says, we need to do this for cellCreation as well, but I think its already taken care of at here https://github.com/openstack-k8s-operators/nova-operator/blob/main/controllers/nova_controller.go#L328-L356

[mrkisaolamb]

Please add some func tests for cell deletion to assert if deletion is working and returning errors for all cells. Also it will be nice to assert what are conditions of nova instance

[openshift-ci]

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https://softwarefactory-project.io/zuul/t/rdoproject.org/buildset/55d93ec55a534c64a74ed0e2e7f7761a

✔️ openstack-meta-content-provider SUCCESS in 47m 42s
❌ nova-operator-kuttl RETRY_LIMIT in 17m 30s
❌ nova-operator-tempest-multinode FAILURE in 22m 11s
❌ nova-operator-tempest-multinode-ceph FAILURE in 23m 05s