Support running iPad apps on arm64 Macs with My Mac (Designed for iPad).

We originally didn't allow flutter run to avoid confusion with macOS-proper development when that platform was not yet in stable (see comment in #84411).

Now that macOS development has been in stable for awhile, and arm64 Macs are far more prevalent, let's enable this to make it easier for developers to debug their app in whatever way Apple supports.

• Show Mac Designed for iPad in device discovery and flutter devices when iOS development is enabled #141290 (this was reverted)
• Support flutter run and flutter drive for Mac Designed for iPad apps on arm64 Macs #141328
• Support flutter build x for Mac Designed for iPad apps on arm64 Macs #141332
• Support flutter install, logs for Mac Designed for iPad apps on arm64 Macs #141333
• [Impeller] Metal validation error when creating textures when run in Designed For iPad mode #139147
• Audit iOS simulator tests in engine and framework to see if this can be used instead

#125741