Allow flutter run to work end-to-end with a UWP device.

Uses win32/ffi for the actual launch of the application, injected via
the native API class. This is structured to avoid a g3 dependency.

Install and amuid require powershell scripts for now.

Actually connecting to the observatory requires running a command in an
elevated prompt. Instructions are presented to the user if a terminal is
attached.

This is a rebased version of https://github.com/flutter/flutter/pull/79684
by @jonahwilliams, updated to remove `NativeApi` and replace is with calls
to `uwptool`.

Part of https://github.com/flutter/flutter/issues/82085

* consolidate all web integration tests under the same shard

Manual plugin roll to account for a rename of the script used to run
analysis.

flutter/engine@3c93ad4...44ba0c7

2021-05-11 chris@bracken.jp Formatting cleanup for CONTRIBUTING.md
(flutter/engine#26080)
2021-05-11 chris@bracken.jp Add uwptool.exe (flutter/engine#26038)
2021-05-11 bkonyi@google.com Manual SDK roll for DevTools SDK
integration (flutter/engine#26075)
2021-05-11 skia-flutter-autoroll@skia.org Roll Skia from 96bc12d19b9e to
7c328b4b42c5 (5 revisions) (flutter/engine#26071)

2021-05-11 iska.kaushik@gmail.com Unique frame number for each frame
(flutter/engine#26021)

In https://github.com/flutter/engine/pull/26075 we rolled the Dart SDK
to the engine. This included updates to parameter names to Iterable.map
and Iterable.expand which triggers lints about renaming method
parameters in CachingIterable.map and CachingIterable.expand.

3c93ad4c5 [web] Resolve OS as iOs for iDevice Safari requesting desktop version of app. (flutter/engine#25957) (#82300)

Re-land:  Allow users to pass in Xcode build settings as env variables to flutter build macos FLUTTER_XCODE_  (#82298)