Merged PR 54492: internal/release/8.0.4xx - merge from public

#### AI description  (iteration 1)
#### PR Classification
This PR merges public updates into the internal release branch, incorporating dependency upgrades, CI pipeline reconfigurations, and improvements to NuGet package verification.

#### PR Summary
The changes synchronize dependency versions and enhance the build and validation processes.
- `eng/common/post-build/nuget-verification.ps1`: Added a new script that downloads and runs the NuGet verification tool to validate package metadata.
- `eng/Version.Details.xml`, `global.json`, and `eng/Versions.props`: Updated dependency versions (e.g., Arcade, Helix, SignTool, XUnitExtensions) and bumped .NET tool versions.
- `eng/common/post-build/nuget-validation.ps1`: Modified to invoke the new verification script instead of manually downloading and running the verification tool.
- YAML pipeline templates (e.g., `.vsts-ci.yml`, `.vsts-pr.yml`, and various job templates): Revised job dependencies by removing deprecated entries, added an OfficialBuildId parameter, and introduced cgIgnoreDirectories support.
- Project files in `src/ApiCompat/...` and `src/GenAPI/...`: Configured to suppress NETSDK1138 warnings for targeting net6.0.
<!-- GitOpsUserAgent=GitOps.Apps.Server.pullrequestcopilot -->

Author: vseanreesermsft

NuGet.config

@@ -25,7 +25,7 @@
     <add key="darc-int-dotnet-runtime-bf170a7" value="https://pkgs.dev.azure.com/dnceng/internal/_packaging/darc-int-dotnet-runtime-bf170a7f/nuget/v3/index.json" />
     <!--  End: Package sources from dotnet-runtime -->
     <!--  Begin: Package sources from dotnet-templating -->
-    <add key="darc-pub-dotnet-templating-fe0130d" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/darc-pub-dotnet-templating-fe0130d7/nuget/v3/index.json" />
+    <add key="darc-pub-dotnet-templating-a2c4545" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/darc-pub-dotnet-templating-a2c45457/nuget/v3/index.json" />
     <!--  End: Package sources from dotnet-templating -->
     <!--  Begin: Package sources from dotnet-windowsdesktop -->
     <add key="darc-int-dotnet-windowsdesktop-2a172fb" value="https://pkgs.dev.azure.com/dnceng/internal/_packaging/darc-int-dotnet-windowsdesktop-2a172fbd/nuget/v3/index.json" />