Revert "[browser] Use Runtime=NET for build tasks in WebAssembly SDK"

[lewing]

This reverts PR #123304 (commit 46c884e).

Reverted Changes

• Restores multi-targeting for Microsoft.NET.Sdk.WebAssembly.Pack.Tasks (net11.0 + net472)
• Restores _WebAssemblySdkTasksTFM\ property and MSBuildRuntimeType-based TFM selection
• Restores \TaskFactory="TaskHostFactory"\ instead of \Runtime="NET"\ for UsingTask declarations
• Restores TFM-specific paths in NuGet package layout

Reason for Revert

Per discussion in dotnet/sdk#52727 (comment):

The \Runtime="NET"\ feature for UsingTask is currently only supported with SDK-style projects (see dotnet/msbuild#12895). Using it in the WebAssembly SDK tasks causes failures when these tasks are invoked from non-SDK-style projects.

Additionally, the .NET Runtime Task Host infrastructure is still maturing, and using it in the SDK at this time is premature. This was causing Blazor test failures in the SDK repo where tasks would crash with \ArgumentNullException\ when the .NET Runtime Task Host couldn't be found.

This revert restores the previous behavior using \TaskFactory="TaskHostFactory"\ with TFM-based task assembly selection, which works reliably across both SDK-style and non-SDK-style projects.

The \Runtime="NET"\ approach can be revisited once MSBuild has broader support for this feature.

Related:

• Enable .NET TaskHost usage for Project types that do not import the base .NET SDK-delivered MSBuild SDK msbuild#12895 - Runtime="NET" only works with SDK-style projects
• [Unhandled Exception]: System.ArgumentNullException: Parameter "projectFile" cannot be null. msbuild#13150 - MSBuild crash when wrapping exceptions (fixed but not yet in preview1)

[lewing]

/backport to release/11.0-preview1

[github-actions]

Started backporting to release/11.0-preview1 (link to workflow run)

[Copilot]

Pull request overview

This PR reverts the previous “[browser] Use Runtime=NET for build tasks in WebAssembly SDK” change to restore the earlier multi-targeted tooling and NuGet layout for Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.

Changes:

• Restore multi-targeting of Microsoft.NET.Sdk.WebAssembly.Pack.Tasks (to $(NetCoreAppToolCurrent) and $(NetFrameworkToolCurrent)) and revert GetFilesToPackage to emit framework-specific assets under tools\<tfm>\.
• Reintroduce _WebAssemblySdkTasksTFM and TaskHostFactory-based <UsingTask> declarations so the appropriate net11.0 vs net472 task assembly is selected based on MSBuildRuntimeType.
• Adjust in-tree build/test infrastructure (WasmApp.InTree.props, trimmingTests.targets) so the Artifacts directory layout and generated project templates again match the restored multi-TFM tools directory structure.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.csproj	Restores multi-targeting and TFM-specific packing of the WebAssembly pack tasks assembly into tools\<tfm>\ in the NuGet package.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Reverts to _WebAssemblySdkTasksTFM-driven task assembly selection and TaskHostFactory-based <UsingTask> declarations, pointing to tools\<tfm>\Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.dll.
src/mono/browser/build/WasmApp.InTree.props	Updates the in-tree tools directory to the configuration-level folder so Browser targets can locate per-TFM task assemblies under that root.
eng/testing/linker/trimmingTests.targets	Updates the WasmSdkPackTasksPath placeholder used in generated trimming test projects to the configuration-level tools directory consistent with the reverted layout.

[github-actions]

@lewing backporting to release/11.0-preview1 failed, the patch most likely resulted in conflicts. Please backport manually!

git am output

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Revert "[browser] Use Runtime=NET for build tasks in WebAssembly SDK (#123304)"
Using index info to reconstruct a base tree...
M	src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets
M	src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.csproj
Falling back to patching base and 3-way merge...
Auto-merging src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets
Auto-merging src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.csproj
CONFLICT (content): Merge conflict in src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks.csproj
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 Revert "[browser] Use Runtime=NET for build tasks in WebAssembly SDK (#123304)"
Error: The process '/usr/bin/git' failed with exit code 128

Link to workflow output

[akoeplinger]

/ba-g failures are unrelated infrastructure issues