Update Microsoft.WindowsAppSDK to 1.6-preview2

[Arlodotexe]

This PR updates our tooling to use Microsoft.WindowsAppSDK 1.6-preview2 and removes prior workarounds only needed for preview1.

• Update WindowsAppSDK to preview2
• Update WindowsSdkPackageVersion for net6 and net8
• Remove workaround for wasdk 1.6 < preview2

Progress towards #205

[michael-hawker]

Do we have a note somewhere or docs about why this is conditional between .NET 6/8?

[Arlodotexe]

See @Sergio0694's comment here.

[Arlodotexe]

Docs can be found here

[Sergio0694]

We should also set DisableRuntimeMarshalling next to where we're setting IsAotCompatible (see here).

[Arlodotexe]

We should also set DisableRuntimeMarshalling next to where we're setting IsAotCompatible (see here).

For reference, docs on this can be found here -> https://learn.microsoft.com/en-us/dotnet/standard/native-interop/disabled-marshalling

[Arlodotexe]

We should also set DisableRuntimeMarshalling next to where we're setting IsAotCompatible (see here).

For reference, docs on this can be found here -> https://learn.microsoft.com/en-us/dotnet/standard/native-interop/disabled-marshalling

Since this is specific to Rive and 1.6 stable is out now, we'll do this in a future PR to keep things moving.