1. Add iOS and macOS migration to mark "last upgraded" Xcode version to 14.3 to prevent `Update to recommended settings` warning.
2. Update iOS and macOS templates to same.
3. Update iOS template to set `BuildIndependentTargetsInParallel` to YES as suggested.  I didn't add a migration for this since it seems like a minor optimization and I don't think it's worth a potentially botched/corrupted migration.
4. Run all example/integration test project to see migrator work.
5. Add some missing test projects to the build shard since I noticed they were missing and I had to build those manually outside `SHARD=build_tests`.

Fixes https://github.com/flutter/flutter/issues/125817
See https://github.com/flutter/flutter/pull/90304 for Xcode 13 example.

* Add flutter_view sample

* Removed platform_services files

* Addressed comments

* update README.md

* Addressed comments.

Update templates and example Xcode project files to indicate they've
been tested for Xcode 8.3 compatibility.

This prevents project re-validation on initial Xcode launch.