Consider making BlazorWebView Android 'fire and forget' disposal on by default

[Eilon]

In #22496 an optional switch was added to make BlazorWebView on Android do fire-and-forget for its disposal instead of blocking, and sometimes causing a deadlock, and thus an app hang.

From user reports it seems that the switch is helpful to anyone who previously experienced a hang without the switch.

What's not clear is whether the switch has any negative effects for apps that were not previously experiencing any problems. And there appears to be one case where setting the switch makes the app behave better, but the app still has a problem.