Enable wrapping of NavigationView/TabView like controls

[kmelmon]

This issue was discovered by Office folks when they attempted to wrap the XAML TwoPaneView. The issue occurs when you have this sort of arrangement:

[WrappedControl]
  [Component /]
  [etc]
[/WrappedControl]

In this situation, the WrappedControl runs layout in XAML which flexbox has no knowledge of. Inside the WrappedControl are react-native components which need flexbox to layout correctly. This doesn't currently work because flexbox is "stomping over" the properties that XAML is supposed to be in control of.

We know of several WinUI controls that behave similarly to TwoPaneView (NavigationView and TabView). So this will be a general problem moving forward if we want to wrap those types of controls.

There does appear to be a way to resolve the conflict - we'd need to let XAML participate in the overall layout process and override flexbox when necessary. Note that this solution would need to take the upcoming Fabric change into consideration - in that world, layout is running off of the UI thread, so letting XAML override becomes more difficult.

This issue is tracking solving this general problem.

[chrisglein]

This is a hard design problem and we don't have an immediate customer that requires this. We need to figure this out, but it can wait a bit (and closer to WinUI3 may help)

[kmelmon]

@jonthysell I thought you should be aware of this issue as you dig into custom view managers. I did some digging into this issue with @sayzenberg and we determined there may be a way to solve this, but it's complicated, and would have an impact on custom view managers. Feel free to chat with me more.

[asklar]

This could be the root cause for asklar/react-native-xaml#67