[platform_interface] Follow-up to plugin platform interface work

[navaronbracke]

Due to the requested priority of #916 (including all of its bugfixes) I've opted to prepare an initial version 5.0.0 beta release.

However, the current beta version still lacks a few things.

• Support Impeller on Android #867
• relanding support for JSQR (if needed)
• provide support for analyzeImage() on the web, where we treat the path as a Blob object url
• adding integration / unit tests to mobile_scanner
• WASM support for the web, since Flutter is about to enable that for its users
  • migration to WASM capable API's is done, but the example app still experiences some issues
  • there are some issues with the camera when using WASM at the moment, this should be fixed on Flutter 3.24 ?
  • [web] move away from using ui_web.platformViewRegistry.registerViewFactory #1126
  • investigate if we can switch to the ZXing WASM version wasm version of zxing for web #1231
• implement scan window for the web using an intersection of points
• provide availableCameras for the web, using the relevant web API
• provide availableCameras for iOS / MacOS
  • provide a static method to query for the available cameras
• Can't close the camera on Web #1087
• support scan window on MacOS, using https://developer.apple.com/documentation/vision/vnimagebasedrequest
• fix the NV21 formats bug on Android
• fix arm64 iOS Simulators support documentation
• migrate iOS to the Vision API, Deprecate MLKit for iOS #1225
• Deduplicate isBarcodeInScanWindow #777

Regarding tests, PR's are welcome to add some of those.
I will be taking on the WASM support work myself.