Allow building a skeleton UWP embedding #70196
Description
This tracks getting a preliminary UWP embedding engine build working, without actually being functional:
- Dart support for a UWP variant
- Buildroot changes
- Skia changes (PR)
- Engine target stub
- Engine CoreWindow implementation Windows: Add CoreWindow implementation of FlutterWindowsView (Flutter#70205) engine#23573
- Changes for engine to link cleanly for AppContainer
- SKIA fix type (branch)
- Second wave of Buildroot changes (PR: Fix linker to enable successful builds of the --winuwp target (#438)): landed, not yet rolled into Flutter engine
- Windows: Fix fml::GetFullHandlePath for WINUWP target (PR: Windows: Fix fml::GetFullHandlePath for WINUWP target)
- ANGLE changes re-land (PR: Reland "Add support for building in Flutter Windows UWP configuration")