[7.0] Fix intellisense xml file selection from 'net' or 'dotnet-plat-ext' (#82554)

* Remove 'net' leaf folder from XmlDocFileRoot.

* Ensure files from both 'net' and 'dotnet-plat-ext' are included in artifacts/bin/docs copy.

* Find the right intellisense xml file from the internal nupkg in either the 'net' or the 'dotnet-plat-ext' folder when packaging.

---------

Co-authored-by: carlossanlop <carlossanlop@users.noreply.github.com>

Author: carlossanlop

Directory.Build.props

@@ -91,7 +91,7 @@
     <IbcOptimizationDataDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsDir)', 'ibc'))</IbcOptimizationDataDir>
     <MibcOptimizationDataDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsDir)', 'mibc'))</MibcOptimizationDataDir>
     <XmlDocDir>$([MSBuild]::NormalizeDirectory('$(ArtifactsBinDir)', 'docs'))</XmlDocDir>
-    <XmlDocFileRoot>$([MSBuild]::NormalizeDirectory('$(NuGetPackageRoot)', 'microsoft.private.intellisense', '$(MicrosoftPrivateIntellisenseVersion)', 'IntellisenseFiles', 'net'))</XmlDocFileRoot>
+    <XmlDocFileRoot>$([MSBuild]::NormalizeDirectory('$(NuGetPackageRoot)', 'microsoft.private.intellisense', '$(MicrosoftPrivateIntellisenseVersion)', 'IntellisenseFiles'))</XmlDocFileRoot>
     <DocsDir>$([MSBuild]::NormalizeDirectory('$(MSBuildThisFileDirectory)', 'docs'))</DocsDir>
     <ManPagesDir>$([MSBuild]::NormalizeDirectory('$(DocsDir)', 'manpages'))</ManPagesDir>
 

eng/packaging.targets

@@ -24,7 +24,10 @@
                                        '$(BuildAllConfigurations)' == 'true' and
                                        '$(DotNetBuildFromSource)' == 'true'">true</GeneratePackageOnBuild>
     <!-- Search for the documentation file in the intellisense package and otherwise pick up the generated one. -->
-    <LibIntellisenseDocumentationFilePath>$(XmlDocFileRoot)1033\$(AssemblyName).xml</LibIntellisenseDocumentationFilePath>
+    <IntellisenseNetFile>$([MSBuild]::NormalizePath('$(XmlDocFileRoot)', 'net', '1033', '$(AssemblyName).xml'))</IntellisenseNetFile>
+    <LibIntellisenseDocumentationFilePath Condition="Exists(IntellisenseNetFile)">$(IntellisenseNetFile)</LibIntellisenseDocumentationFilePath>
+    <IntellisenseDotNetPlatExtFile Condition="'$(LibIntellisenseDocumentationFilePath)' == ''">$([MSBuild]::NormalizePath('$(XmlDocFileRoot)', 'dotnet-plat-ext', '1033', '$(AssemblyName).xml'))</IntellisenseDotNetPlatExtFile>
+    <LibIntellisenseDocumentationFilePath Condition="'$(LibIntellisenseDocumentationFilePath)' == '' and Exists($(IntellisenseDotNetPlatExtFile))">$(IntellisenseDotNetPlatExtFile)</LibIntellisenseDocumentationFilePath>
     <UseIntellisenseDocumentationFile Condition="'$(UseIntellisenseDocumentationFile)' == '' and Exists('$(LibIntellisenseDocumentationFilePath)')">true</UseIntellisenseDocumentationFile>
   </PropertyGroup>
 

eng/restore/docs.targets

@@ -9,7 +9,7 @@
           AfterTargets="Restore">
 
     <ItemGroup>
-      <DocFile Include="$(XmlDocFileRoot)**\*.xml"/>
+      <DocFile Include="$(XmlDocFileRoot)\net\**\*.xml;$(XmlDocFileRoot)\dotnet-plat-ext\**\*.xml"/>
       <DocFile>
         <!-- trim off slash since it differs by platform and we need to do a string compare -->
         <LCID>$([System.String]::new('%(RecursiveDir)').TrimEnd('\/'))</LCID>
@@ -35,7 +35,7 @@
     </ItemGroup>
 
     <Error Condition="'%(DocFile.Culture)' == 'unknown'" Text="Unknown language folder '%(LCID)' for doc files '@(DocFile)'" />
-    
+
     <Copy SourceFiles="@(DocFile)"
           DestinationFiles="$(XmlDocDir)\%(SubFolder)%(FileName)%(Extension)"
           SkipUnchangedFiles="true"