Strip all package types from inner multi-rid tool packages so they don't appear on search-based experiences

[baronfel]

Fixes #49615

The outer tool package will have all package types (McpServer, DotnetTool), but the inner packages will just have DotnetToolRidPackage. This prevents experiences like the MCP registry, which search based on "has PackageType of McpServer", from reporting the inner packages.

[Copilot]

Pull Request Overview

This PR ensures that inner RID-specific tool packages only carry the DotnetToolRidPackage type while the outer tool package retains all specified package types, preventing inner packages from appearing in search-based experiences.

• Extended TestToolBuilder to accept and embed additional package types into its package identifier.
• Added an end-to-end test StripsPackageTypesFromInnerToolPackages to validate package types on both inner and outer tool packages.
• Updated Microsoft.NET.PackTool.targets to conditionally set PackageType only for outer (DotnetTool) vs. inner (DotnetToolRidPackage) packages.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
test/Microsoft.DotNet.PackageInstall.Tests/TestToolBuilder.cs	Added AdditionalPackageTypes setting and enhanced GetIdentifier
test/Microsoft.DotNet.PackageInstall.Tests/EndToEndToolTests.cs	New E2E test covering package-type stripping and related helpers
src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.PackTool.targets	Conditional logic for outer vs. inner tool package type assignment

Comments suppressed due to low confidence (3)

test/Microsoft.DotNet.PackageInstall.Tests/EndToEndToolTests.cs:358

• The assertion message only mentions 'DotnetTool' while the test expects DotnetTool plus additional types; consider updating the message to reference all expected package types or generalize it.

                .And.BeEquivalentTo(expectedPackageTypes, "The PackageType should be 'DotnetTool'.");

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.PackTool.targets:388

• MSBuild Condition expressions require == for equality checks; using a single = will not evaluate as intended. Update to Condition="$(_ToolPackageType) == 'DotnetTool'".

    <AddPackageType Condition="$(_ToolPackageType) = 'DotnetTool'" CurrentPackageType="$(PackageType)" PackageTypeToAdd="$(_ToolPackageType)">

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.PackTool.targets:392

• MSBuild Condition expressions require == for equality; update to Condition="$(_ToolPackageType) == 'DotnetToolRidPackage'" so the inner package rule applies correctly.

    <PropertyGroup Condition="$(_ToolPackageType) = 'DotnetToolRidPackage'">