Catalyst nuget package .NET changes only (#20424)

### Description
<!-- Describe your changes. -->

#20418

Add back Catalyst changes only for now.

### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->

Co-authored-by: rachguo <[email protected]>

csharp/src/Microsoft.ML.OnnxRuntime/Microsoft.ML.OnnxRuntime.csproj

@@ -39,7 +39,7 @@
   <PropertyGroup Condition="('$(OrtPackageId)' == 'Microsoft.ML.OnnxRuntime' OR
                              '$(OrtPackageId)' == 'Microsoft.ML.OnnxRuntime.Azure') AND
                             '$(IncludeMobileTargets)' == 'true'">
-    <MobileTargets>$(MobileTargets);net6.0-android;net6.0-ios</MobileTargets>
+    <MobileTargets>$(MobileTargets);net6.0-android;net6.0-ios;net6.0-maccatalyst</MobileTargets>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(OrtPackageId)' == 'Microsoft.ML.OnnxRuntime.Training' AND
@@ -121,9 +121,9 @@
     <IsAndroidTarget Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android' OR
                                 $(TargetFramework.StartsWith('monoandroid'))">true</IsAndroidTarget>
     <IsIOSTarget Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'ios' OR
+                            $([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst' OR
                             $(TargetFramework.StartsWith('xamarinios'))">true</IsIOSTarget>
-    <IsMacTarget Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'macos' OR
-                            $([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'maccatalyst'">true</IsMacTarget>
+    <IsMacTarget Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'macos'">true</IsMacTarget>
   </PropertyGroup>
 
   <!-- Enable training APIs for the build. The native package must be

csharp/src/Microsoft.ML.OnnxRuntime/targets/net6.0-maccatalyst/README.md

@@ -0,0 +1,3 @@
+### Notes for maccatalyst .NET targets:
+
+We only add a blank file for the target framework folder here and thus will be including blank TFM under build/ and buildTransitive/ in the Nuget package. The reason is for Mac Catalyst platform, it directly will resolve the xcframework from the runtimes/native/ios folder based on this [RuntimeidentifierGraph](https://github.com/dotnet/sdk/blob/main/src/Layout/redist/PortableRuntimeIdentifierGraph.json#L300-L304)

tools/ci_build/github/azure-pipelines/c-api-noopenmp-packaging-pipelines.yml

@@ -675,7 +675,7 @@ stages:
       inputs:
         targetType: 'inline'
         script: |
-          dotnet workload install android ios
+          dotnet workload install android ios maccatalyst
         workingDirectory: '$(Build.SourcesDirectory)\csharp'
 
     - task: MSBuild@1

tools/ci_build/github/azure-pipelines/templates/c-api-cpu.yml

@@ -409,7 +409,7 @@ stages:
       inputs:
         targetType: 'inline'
         script: |
-          dotnet workload install android ios
+          dotnet workload install android ios maccatalyst
         workingDirectory: '$(Build.SourcesDirectory)\csharp'
 
     - task: MSBuild@1

tools/nuget/generate_nuspec_for_native_nuget.py

@@ -280,6 +280,10 @@ def generate_dependencies(xml_text, package_name, version):
             xml_text.append('<group targetFramework="net6.0-macos12.3">')
             xml_text.append('<dependency id="Microsoft.ML.OnnxRuntime.Managed"' + ' version="' + version + '"/>')
             xml_text.append("</group>")
+            # Support net6.0-maccatalyst
+            xml_text.append('<group targetFramework="net6.0-maccatalyst14.0">')
+            xml_text.append('<dependency id="Microsoft.ML.OnnxRuntime.Managed"' + ' version="' + version + '"/>')
+            xml_text.append("</group>")
         # Support Native C++
         if include_dml:
             xml_text.append('<group targetFramework="native">')
@@ -989,6 +993,20 @@ def generate_files(line_list, args):
                 args.package_name + ".targets",
             )
 
+            net6_maccatalyst_source_targets = os.path.join(
+                args.sources_path,
+                "csharp",
+                "src",
+                "Microsoft.ML.OnnxRuntime",
+                "targets",
+                "net6.0-maccatalyst",
+                "_._",
+            )
+
+            net6_maccatalyst_target_targets = os.path.join(
+                args.sources_path, "csharp", "src", "Microsoft.ML.OnnxRuntime", "targets", "net6.0-maccatalyst", "_._"
+            )
+
             net6_macos_source_targets = os.path.join(
                 args.sources_path, "csharp", "src", "Microsoft.ML.OnnxRuntime", "targets", "net6.0-macos", "targets.xml"
             )
@@ -1006,6 +1024,7 @@ def generate_files(line_list, args):
             os.system(copy_command + " " + xamarinios_source_targets + " " + xamarinios_target_targets)
             os.system(copy_command + " " + net6_android_source_targets + " " + net6_android_target_targets)
             os.system(copy_command + " " + net6_ios_source_targets + " " + net6_ios_target_targets)
+            os.system(copy_command + " " + net6_maccatalyst_source_targets + " " + net6_maccatalyst_target_targets)
             os.system(copy_command + " " + net6_macos_source_targets + " " + net6_macos_target_targets)
 
             files_list.append("<file src=" + '"' + monoandroid_target_targets + '" target="build\\monoandroid11.0" />')
@@ -1029,6 +1048,15 @@ def generate_files(line_list, args):
             files_list.append(
                 "<file src=" + '"' + net6_ios_target_targets + '" target="buildTransitive\\net6.0-ios15.4" />'
             )
+            files_list.append(
+                "<file src=" + '"' + net6_maccatalyst_target_targets + '" target="build\\net6.0-maccatalyst14.0" />'
+            )
+            files_list.append(
+                "<file src="
+                + '"'
+                + net6_maccatalyst_target_targets
+                + '" target="buildTransitive\\net6.0-maccatalyst14.0" />'
+            )
 
             files_list.append("<file src=" + '"' + net6_macos_target_targets + '" target="build\\net6.0-macos12.3" />')
             files_list.append(