Fixes to improve IDE usage

The `Set Startup Project` button isn't working unless we remove:

    <ProjectCapability Include="Maui" />

I made a new `$(_ExcludeMauiProjectCapability)` MSBuild property, so
we can set an `%_ExcludeMauiProjectCapability%` environment variable
in `dogfood.ps1`.

I also removed some places we were setting MacCatalyst
`$(RuntimeIdentifier)` that was confusing the IDE.
`$(RuntimeIdentifier)` does not need to be set in library projects,
only app projects.

.nuspec/Microsoft.Maui.Controls.targets

@@ -19,7 +19,7 @@
 
 	<ItemGroup>
 		<ProjectCapability Include="XamarinForms" />
-		<ProjectCapability Include="Maui" />
+		<ProjectCapability Include="Maui" Condition="'$(_ExcludeMauiProjectCapability)' != 'true'" />
 	</ItemGroup>
 
 	<!-- Check Tasks ABI and other validations -->

eng/dogfood.ps1

@@ -61,6 +61,7 @@ $oldDOTNET_ROOT=$env:DOTNET_ROOT
 $oldDOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=$env:DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR
 $oldDOTNET_MULTILEVEL_LOOKUP=$env:DOTNET_MULTILEVEL_LOOKUP
 $oldMSBuildEnableWorkloadResolver=$env:MSBuildEnableWorkloadResolver
+$old_ExcludeMauiProjectCapability=$env:_ExcludeMauiProjectCapability
 $oldPATH=$env:PATH
 
 try {
@@ -78,6 +79,9 @@ try {
     # This enables workload support inside the IDE
     $env:MSBuildEnableWorkloadResolver=$true
 
+    # This disables the Maui @(ProjectCapability), a temporary workaround for 16.9
+    $env:_ExcludeMauiProjectCapability=$true
+
     # Put our local dotnet.exe on PATH first so Visual Studio knows which one to use
     $env:PATH=($env:DOTNET_ROOT + ";" + $env:PATH)
 
@@ -90,6 +94,7 @@ try {
         $env:DOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR=$oldDOTNET_MSBUILD_SDK_RESOLVER_CLI_DIR
         $env:DOTNET_MULTILEVEL_LOOKUP=$oldDOTNET_MULTILEVEL_LOOKUP
         $env:MSBuildEnableWorkloadResolver=$oldMSBuildEnableWorkloadResolver
+        $env:_ExcludeMauiProjectCapability=$old_ExcludeMauiProjectCapability
         $env:PATH=$oldPATH
     }
 }

src/Compatibility/Core/src/Android.FormsViewGroup/Compatibility.Android.FormsViewGroup-net6.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net6.0-android</TargetFrameworks>
+    <TargetFramework>net6.0-android</TargetFramework>
     <RootNamespace>Microsoft.Maui.Controls.Compatibility.Android</RootNamespace>
     <AssemblyName>Microsoft.Maui.Controls.Compatibility.Android.FormsViewGroup</AssemblyName>
     <OutputType>Library</OutputType>

src/Compatibility/Core/src/Compatibility-net6.csproj

@@ -4,8 +4,6 @@
     <RootNamespace>Microsoft.Maui.Controls.Compatibility</RootNamespace>
     <AssemblyName>Microsoft.Maui.Controls.Compatibility</AssemblyName>
     <Nullable>disable</Nullable>
-    <RuntimeIdentifier Condition=" '$(TargetFramework)' == 'net6.0-ios' ">ios-x64</RuntimeIdentifier>
-    <RuntimeIdentifier Condition=" '$(TargetFramework)' == 'net6.0-maccatalyst' ">maccatalyst-x64</RuntimeIdentifier>
     <EnableDefaultItems>false</EnableDefaultItems>
     <AndroidRoot>Android\</AndroidRoot>
     <iOSRoot>iOS\</iOSRoot>

src/Core/src/Core-net6.csproj

@@ -4,8 +4,6 @@
     <RootNamespace>Microsoft.Maui</RootNamespace>
     <AssemblyName>Microsoft.Maui</AssemblyName>
     <Nullable>enable</Nullable>
-    <RuntimeIdentifier Condition=" '$(TargetFramework)' == 'net6.0-ios' ">ios-x64</RuntimeIdentifier>
-    <RuntimeIdentifier Condition=" '$(TargetFramework)' == 'net6.0-maccatalyst' ">maccatalyst-x64</RuntimeIdentifier>
   </PropertyGroup>
   <PropertyGroup>
     <PackageId>Microsoft.Maui.Core</PackageId>

src/Package/Package-net6.csproj

@@ -5,8 +5,6 @@
 		<RootNamespace>Microsoft.Maui</RootNamespace>
 		<AssemblyName>Microsoft.Maui.Package</AssemblyName>
 		<Nullable>enable</Nullable>
-		<RuntimeIdentifier Condition=" '$(TargetFramework)' == 'net6.0-ios' ">ios-x64</RuntimeIdentifier>
-		<RuntimeIdentifier Condition=" '$(TargetFramework)' == 'net6.0-maccatalyst' ">maccatalyst-x64</RuntimeIdentifier>
 		<IncludeBuildOutput>False</IncludeBuildOutput>
 		<NoWarn>$(NoWarn);NU5100;NU5128;</NoWarn>
 	</PropertyGroup>