Work around XAML Islands issues with TextCommandBarFlyout

[rozele]

As reported in microsoft/microsoft-ui-xaml#5341, the singleton TextCommandBarFlyout for the XAML TextBox and TextBlock components are limited to one window. When the flyout opens on a different window after already being opened on another, the first window the flyout was opened on gets focus, and the flyout is immediately closed. This change creates a TextCommandBarFlyout per TextInput native view and per selection TextBlock native view.

Additionally, it includes logic to work around an issue with the Proofing sub-menu flyout, which crashes due to an animation bug on Windows 10 versions lower than 21H1.

Microsoft Reviewers: Open in CodeFlow

[rozele]

Easy way to repro these issues in playground-win32:

1. Comment out the code that creates a new thread for new windows in Playground-win32.cpp:
   https://github.com/microsoft/react-native-windows/blob/main/packages/playground/windows/playground-win32/Playground-Win32.cpp#L133
2. For the multi-window issue, load two instances of RNTester and attempt to show the context menu on each window. Note that the first window will get focused when you attempt to show the context menu on the second.
3. For the Proofing menu crash, open RNTester, navigate to a TextInput field with autocorrect, type text that would have text suggestions, open the context menu and move the mouse around to open and close the proofing menu flyout multiple times on Windows 10 < 21H1.

[NickGerleman]

@rozele is this one ready for merge?

[rozele]

@NickGerleman - going to implement @lyahdav's suggestion, then this should be ready 😅

Update: now it should be ready :)

[lyahdav]

@NickGerleman Any update on this? It's blocking another PR I'd like to submit.

[NickGerleman]

Sorry, missed the notification that it is ready for merge. I don't think GH updates send notifications, so feel free to give me a mention is there is a change to an older PR, and I will take a look.