[camera] Fix ImageStream ImageFormatGroup is Ignored in iOS (flutter#…

…4519)

[video_player] Added the setCaptionOffset (flutter#3275)

[file_selector] Endorse Windows (flutter#4696)

[file_selector] Add Windows support (flutter#4424)

[camera_platform_interface] Fix asynchronous exceptions handling of t…

…he `initializeCamera` method (flutter#4660)

[webview_flutter_web] Explain web registration (flutter#4668)

The README instructions currently use the standard description of using
an unendorsed implementation of a federated package, which assumes
auto-registration. Because `webview_flutter_web` doesn't use
autoregistration due to the current structural issues in
`webview_flutter`'s federation, those instructions aren't complete.

This adds an explanation of registering the implementation, including an
example of using conditional imports for multi-platform projects.

[image_picker] Improves documentation around the destruction of the M…

…ainActivity. (flutter#4672)

[camera]fix crash due to race condition in dispatch queue (flutter#4619)

[video_player] Update iOS README section (flutter#4688)

Removes the suggestion to just use the strongly-discouraged-by-Apple `NSAllowsArbitraryLoads`, and instead links to Apple's docs about the various options.

This removes the example entirely since there's no one-size-fits-all case; some clients would just need `NSExceptionDomains` (this seems likely to be the more common case?), others `NSAllowsArbitraryLoadsForMedia`, others `NSAllowsArbitraryLoadsForMedia`+` NSAllowsArbitraryLoads` (to support iOS 9). Given that the narrowest option that works for someone is the best option, having them actually research the options is the best thing to steer people toward, even if that's not as simple as "copy and paste the following".

Also opportunistically removes a couple of obsolete items:
- An incorrect note that `android.permission.INTERNET` is likely already present in the
  main Android manifest file; it was made debug-only a while ago.
- An old note about web version compatibility; we only support Flutter 2+ now anyway.

[video_player] Remove KVO observer on AVPlayerItem on iOS (flutter#4683)