Add generateCode target

[JoshLove-msft]

Fixes #49545

[Copilot]

Pull Request Overview

This PR introduces a new MSBuild GenerateCode target for TypeSpec-based client generation and adjusts the Event Grid Namespaces library to opt out of AutoRest and consume shared core sources manually.

• Expose a GenerateCode target when IncludeAutorestDependency is disabled and a tsp-location.yaml file is present
• Toggle AutoRest package inclusion via IncludeAutorestDependency and wire up shared Azure Core source files in the Namespaces project
• Remove a codegen suppression attribute that may no longer be necessary

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
sdk/eventgrid/Azure.Messaging.EventGrid.Namespaces/src/properties/AssemblyInfo.cs	Removed CodeGenSuppressType entry
sdk/eventgrid/Azure.Messaging.EventGrid.Namespaces/src/Azure.Messaging.EventGrid.Namespaces.csproj	Added IncludeAutorestDependency toggle and shared core includes
eng/Directory.Build.Common.targets	Switched AutoRest package condition and added GenerateCode target
eng/Directory.Build.Common.props	Defaulted IncludeAutorestDependency for client libraries

Comments suppressed due to low confidence (3)

sdk/eventgrid/Azure.Messaging.EventGrid.Namespaces/src/properties/AssemblyInfo.cs:10

• Removing this CodeGenSuppressType attribute may re-enable generation for a type that was intentionally suppressed. Confirm whether this suppression is obsolete or if it needs to be relocated/updated in the code-gen configuration.

-[assembly: CodeGenSuppressType("MessagingEventGridNamespacesClientBuilderExtensions")]

eng/Directory.Build.Common.targets:454

• [nitpick] The error message is a bit verbose and references internal property names. Consider simplifying to something like: "Temporary TypeSpec inputs missing; run dotnet build /t:GenerateCode /p:SaveInputs=true once without SkipSync."

<Error Text="You used skipped sync but didn't have the TempTypeSpecFiles in your project directory.  Please run 'dotnet build /t:GenerateCode /p:SaveInputs=true' without SkipSync first at least once" Condition="'$(SkipSync)' == 'true' AND !Exists('$(MSBuildProjectDirectory)/../TempTypeSpecFiles')" />

eng/Directory.Build.Common.targets:453

• [nitpick] The new GenerateCode MSBuild target adds important code-gen behavior. Consider adding automated CI tests or integration steps to validate this target under various flags (SkipSync, SaveInputs, presence of TypeSpecInput).

<Target Name="GenerateCode" Condition="'$(IncludeAutorestDependency)' != 'true' AND '$(TypeSpecInput)' != ''">