Don't overwrite pinned assembly versions in servicing

There are eight packable projects that pin their assembly version for .NET
Framework compatibility. The incremental package servicing
infrastructure didn't check if the assembly version is pinned and always
changed it.

As an example, System.Speech pins its assembly version to 4.0.0.0 but
that version gets overwritten during servicing. I.e. for .NET 7 the
version would then change to "7.0.0.$(ServicingVersion)" which is
incorrect.

Please find the full list of impacted assemblies below:
- System.ComponentModel.Composition
- System.DirectoryServices
- System.DirectoryServices.AccountManagement
- System.DirectoryServices.Protocols
- System.Management
- System.Reflection.Context
- System.Runtime.Caching
- System.Speech

eng/packaging.targets

@@ -48,8 +48,10 @@
     <_IsWindowsDesktopApp Condition="$(WindowsDesktopCoreAppLibrary.Contains('$(AssemblyName);'))">true</_IsWindowsDesktopApp>
     <_IsAspNetCoreApp Condition="$(AspNetCoreAppLibrary.Contains('$(AssemblyName);'))">true</_IsAspNetCoreApp>
     <_AssemblyInTargetingPack Condition="('$(IsNETCoreAppSrc)' == 'true' or '$(IsNetCoreAppRef)' == 'true' or '$(_IsAspNetCoreApp)' == 'true' or '$(_IsWindowsDesktopApp)' == 'true') and '$(TargetFrameworkIdentifier)' != '.NETFramework'">true</_AssemblyInTargetingPack>
-    <!-- Assembly version do not get updated in non-netfx ref pack assemblies. -->
-    <AssemblyVersion Condition="'$(_AssemblyInTargetingPack)' != 'true'">$(MajorVersion).$(MinorVersion).0.$(ServicingVersion)</AssemblyVersion>
+    <!-- The assembly version gets updated when
+      - it isn't already set (i.e. it could be pinned to a specific version for .NET Framework compatibility) and
+      - the assembly isn't part of a targeting pack (always true for .NET Framework). -->
+    <AssemblyVersion Condition="'$(AssemblyVersion)' == '' and '$(_AssemblyInTargetingPack)' != 'true'">$(MajorVersion).$(MinorVersion).0.$(ServicingVersion)</AssemblyVersion>
   </PropertyGroup>
 
   <ItemGroup>

src/libraries/System.ComponentModel.Composition/Directory.Build.props

@@ -1,6 +1,9 @@
 <Project>
   <Import Project="..\Directory.Build.props" />
   <PropertyGroup>
+    <!-- this assembly is inbox in desktop, do not version it unless you
+         plan on shipping a new desktop version out of band. Instead add API
+         to a different assembly. -->
     <AssemblyVersion>4.0.0.0</AssemblyVersion>
     <StrongNameKeyId>ECMA</StrongNameKeyId>
   </PropertyGroup>

src/libraries/System.Data.DataSetExtensions/Directory.Build.props

@@ -1,8 +1,6 @@
 <Project>
   <Import Project="..\Directory.Build.props" />
   <PropertyGroup>
-    <!-- AssemblyVersion is frozen to that which originally shipped in 2.1 -->
-    <AssemblyVersion>4.0.0.0</AssemblyVersion>
     <StrongNameKeyId>ECMA</StrongNameKeyId>
   </PropertyGroup>
 </Project>

src/libraries/System.Reflection.Context/Directory.Build.props

@@ -1,6 +1,9 @@
 <Project>
   <Import Project="..\Directory.Build.props" />
   <PropertyGroup>
+    <!-- this assembly is inbox in desktop, do not version it unless you
+         plan on shipping a new desktop version out of band. Instead add API
+         to a different assembly. -->
     <AssemblyVersion>4.0.3.0</AssemblyVersion>
     <StrongNameKeyId>ECMA</StrongNameKeyId>
   </PropertyGroup>

src/libraries/System.Reflection.Context/ref/System.Reflection.Context.csproj

@@ -1,9 +1,5 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <!-- this assembly is inbox in desktop, do not version it unless you
-         plan on shipping a new desktop version out of band. Instead add API
-         to a different assembly. -->
-    <AssemblyVersion>4.0.0.0</AssemblyVersion>
     <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppPrevious);$(NetCoreAppMinimum);netstandard2.1;netstandard2.0</TargetFrameworks>
   </PropertyGroup>