[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 facebook@f1925c2 to fix tests running on the new architecture

Test Plan:

CI should pass