.NET MAUI 9: Compiled binding warnings disabled

[davidbritch]

In .NET MAUI 9, x:DataType warnings will be disabled. However, the behaviour can be opted back into by setting the $(MauiStrictXamlCompilation) build property to true. This strict compilation will remain enabled by default for NativeAOT.

https://github.com/dotnet/maui/pull/21418

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Associated WorkItem - 314389

[simonrozsival]

The warnings were disabled in a .NET 8 servicing release but they should be enabled by default in .NET 9. The reason why we disabled them was that they were introduced in a .NET 8 servicing release and started breaking customers' app builds.