[ACM-14235]: Ensure CMO ConfigMap is reconciled on any event

[philipgough]

Backport of https://github.com/stolostron/multicluster-observability-operator/pull/1612

1. Adds an integration test for merging of CMO ConfigMap with other clients
2. Adds the Delete event to the Watch for CMO ConfigMap
3. Explicitly adds the CMO ConfigMap reference to the filtered cache

[sonarcloud[bot]]

Quality Gate failed

Failed conditions
B Maintainability Rating on New Code (required ≥ A)

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[openshift-ci[bot]]

@philipgough: The following test 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/sonarcloud	2453d40f74b5f5ef4c98b3880d10ffec46405092	link	true	/test sonarcloud

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[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jacobbaungard, philipgough

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/stolostron/multicluster-observability-operator/blob/release-2.10/OWNERS)~~ [jacobbaungard,philipgough] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment