Initial iOS support

[ZacSweers]

This does an initial integration of support for iOS in our core artifacts. This is very much intended just to be a toe-hold and not anything meaningful or commitment, but rather a step similar to when we first moved into multiplatform where it can help keep the door open for later work by keeping us honest in our implementation of circuit internals cross-platform friendly now.

This does a bunch of that ground work, namely around preparing the counter sample for this and making some needed infra changes in the core artifacts to support it.

• Switch to using a multiplatform UUID library in backstack. Using the sort of canonical one in the community until Kotlin adds one to the stdlib (https://youtrack.jetbrains.com/issue/KT-31880).
• Don't use java reflection in common code
• Set up ios (which includes iosX64 and iosArm64) and iosSimulatorArm64 (needed for simulator runs) in projects + actual declarations where needed
  • I don't know what Screen will look like in iOS. There's NSCoder maybe? Saving for future work.
  • Promote ContentWithOverlays to commonMain.
  • iOS rememberRetained is also inert like on JVM.
• Started an iOS Counter app and dir. This is super basic and uses a KMM circuit presenter + SwiftUI. It does not try to do a full CircuitContent or anything related. Most relevant bits are in ContentView.swift and SwiftSupport.kt.
• The multiplatform counter presenter now produces a swift framework for use in the above app. Not sure if we wanna make that sample use compose iOS's UI or try it with swift UI or do both.

Simulator.Screen.Recording.-.iPhone.14.Pro.-.2023-04-29.at.13.50.12.mp4

[ZacSweers]

Currently stuck on JetBrains/compose-multiplatform#3088 with the iOS Counter app sample, but everything else looks like it's working. Wanna clean up some of the repetitive bits

[ZacSweers]

Once #615 is in, then we don't need to maintain the separate Dispatchers.IO expect/actual since that version of coroutines introduces it 👍. Not worried about waiting for that PR though due to the androidx test bug