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**Related issue:** For #40015
* Moves repeated empty mocks into a new `setupEmptyGitOpsMocks` method
* Adds new "deprecation" tests:
* In TestGitOpsFullGlobal, TestGitOpsFullTeam and
TestGitOpsFullGlobalAndTeam tests "kitchen sink" with both new and
deprecated keys
* Added keys and checks to verify `setup_experience`,
`apple_business_manager` and `volume_purchasing_program` configs
* Consolidated map of deprecated -> new GitOps keys in one place