Rename runner-agnostic SDKCustomXUnit* Helix infrastructure to a runner-neutral name

[Evangelink]

Fixes #55094

What

Renames the runner-agnostic Helix work-item pipeline from xUnit-specific names to runner-neutral ones. After the xUnit → MSTest/MTP migration, this infrastructure is no longer xUnit-specific (it already detects MTP projects via IsMTPProject/GetIsMTPProject and handles TRX reporting), so the names were misleading. This is a naming/clarity cleanup only — no functional change intended.

Changes

Old	New
test/xunit-runner/	test/test-runner/
XUnitRunner.targets / XUnitPublish.targets	TestRunner.targets / TestPublish.targets
SDKCustomCreateXUnitWorkItemsWithTestExclusion (class + file + UsingTask)	SDKCustomCreateTestWorkItemsWithTestExclusion
SDKCustomXUnitProject item, XUnitWorkItemTimeout, SDKCustomXUnit* props, targets Restore/Build/CreateSDKCustomXUnit*, task params XUnitProjects/XUnitArguments/XUnitWorkItems	SDKCustomTest* / TestWorkItemTimeout / Test* equivalents
xunit comment references in AssemblyScheduler.cs, AwaitableProcess.cs	runner-neutral wording

File/folder renames use git mv to preserve history. The compiled UsingTask TaskName=… declaration in TestRunner.targets was kept in sync with the renamed task class.

Left intentionally untouched:

• Microsoft.DotNet.SdkCustomHelix.Sdk namespace (already runner-neutral).
• eng/common/** (Arcade-vendored — out of scope per the issue).
• The pre-existing $(SDKCustomTestArgument) singular-vs-plural mismatch (was $(SDKCustomXUnitArgument)), to avoid any behavior change.

Does the custom infra actually differ from Arcade's Helix SDK?

The issue asked to confirm this. Compared against Arcade main (src/Microsoft.DotNet.Helix/Sdk/): yes, it differs substantially — the fork is justified, Arcade has not caught up.

• CreateXUnitWorkItemsWithTestExclusion.cs and AssemblyScheduler.cs do not exist in Arcade — they were never contributed upstream.
• Sharding is SDK-only: Arcade has no AssemblyScheduler, no BaseMethodLimit/MethodLimitMultiplier partitioning, no per-shard --filter.
• Arcade's MTP support is a different model: a separate MTPProject item type + CreateMTPWorkItems that emits dotnet exec --roll-forward Major --runtimeconfig … --depsfile … and deliberately omits --report-trx/--diagnostic/--ignore-exit-code 8. The SDK unifies MTP + VSTest under one item type and emits those itself, conditioned on build-time detection.
• Different non-MTP engine: SDK uses VSTest (dotnet test + --blame-hang); Arcade uses legacy xunit.console.dll.
• SDK-only extras: macOS codesign+entitlements, xUnit v3 apphost chmod +x, RID-qualified publish + CI pre-restore, AdditionalPayloadDir, DOTNET_SDK_TEST_EXECUTION_DIRECTORY / …MSBUILDSDKRESOLVER_FOLDER, .netfx identity suffix.

Validation

• HelixTasks.csproj builds clean (0 warnings, 0 errors).
• As noted in the issue, the rename touches a compiled MSBuild task whose UsingTask name must match the class name exactly, and is fully validated only by a green Helix run. Requesting infra-owner review.

Risk

Low-to-medium. A mistake would manifest silently as tests not being scheduled on Helix; needs a full green Helix run to confirm.

[Copilot]

Pull request overview

This PR renames the SDK’s Helix “custom work item” MSBuild infrastructure from xUnit-specific identifiers to runner-neutral Test*/SDKCustomTest* naming, reflecting the post-migration reality where the pipeline handles multiple runner styles (including MTP/TRX).

Changes:

• Renames Helix scheduling item/property/target names in test/UnitTests.proj and updates the imported runner targets path.
• Renames the compiled MSBuild task SDKCustomCreate*WorkItemsWithTestExclusion and updates the UsingTask/parameter names accordingly.
• Renames/updates runner/publish target files and tweaks wording in a couple of comments to be runner-neutral.

Show a summary per file

File	Description
test/UnitTests.proj	Updates Helix scheduling item/property names (SDKCustomTestProject, TestWorkItemTimeout) and imports the renamed runner targets.
test/test-runner/TestRunner.targets	Renames properties/targets/tasks to SDKCustomTest* and updates the work item creation task invocation.
test/test-runner/TestPublish.targets	Runner-neutral publish helper targets (PublishWithOutput, MTP/TRX detection query targets).
test/Microsoft.DotNet.HotReload.Test.Utilities/AwaitableProcess.cs	Updates comment reference to the renamed work-item timeout property.
test/HelixTasks/SDKCustomCreateTestWorkItemsWithTestExclusion.cs	Renames the MSBuild task class and its public MSBuild parameters/outputs to Test*.
test/HelixTasks/AssemblyScheduler.cs	Updates comments to runner-neutral wording (with a couple of doc/comment fixes suggested).

Copilot's findings

Comments suppressed due to low confidence (1)

test/test-runner/TestRunner.targets:12

• SDKCustomTestArguments is given a default value here, but the task invocation later passes TestArguments="$(SDKCustomTestArgument)" (singular). Currently SDKCustomTestArgument is not defined anywhere in the repo, so this default likely never takes effect and the property name may be a typo/leftover.

• Files reviewed: 5/6 changed files
• Comments generated: 3

[MichaelSimons]

I personally think SDKCustomCreateTestWorkItemsWithTestExclusion is unwieldy but that is an existing problem. CreateHelixTestWorkItems would be better IMO.

[Evangelink]

I personally think SDKCustomCreateTestWorkItemsWithTestExclusion is unwieldy but that is an existing problem. CreateHelixTestWorkItems would be better IMO.

Merging as-is as PR is green and I'll do a follow-up.