[CI] Update Build Matrix

[Saadnajmi]

Summary:

Update the CI matrix for React Native macOS. This is a large refactoring of our Azure Pipelines YML. Namely:

• All of our PR pipelines are combined and split into stages.
• We use a compile time matrix instead of a run time for splitting up the "Build RNTester N different ways" tests
• We make several fixes to ensure we can build visionOS in CI (named xrOS for brevity, and also because that's the SDK name). We don't run tests on visionOS yet
• Cherry pick https://github.com/facebook/react-native/commit/f1925c2668ceb96812a6a82db8cda9da787306f4 to fix tests running on the new architecture

Test Plan:

CI should pass

[Saadnajmi]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).