[release/8.0][browser] Disable debugger tests on CI (#108178)

[akoeplinger]

Backport of #108178 to release/8.0-staging

Fixes#128130

[akoeplinger]

Test-only change that we did in main already, marking Servicing-approved.

[dotnet-policy-service]

Tagging subscribers to this area: @steveisok, @thaystg, @dotnet/dotnet-diag
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR backports the change to stop running the Mono WebAssembly debugger test suite on CI by removing its Helix submission plumbing and pipeline legs, addressing CI instability/failures described in #128130.

Changes:

• Remove Azure Pipelines jobs/templates that schedule Wasm debugger tests (including extra-platform legs and default path subset evaluation).
• Remove the Helix “wasmdebuggertests” scenario wiring in sendtohelix.proj and related wasm targets/project configuration.
• Remove Makefile targets used to build/submit Wasm debugger tests to Helix.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/mono/wasm/Makefile	Removes Helix build/submit targets for Wasm debugger tests.
src/mono/wasm/debugger/Wasm.Debugger.Tests/wasm.helix.targets	Deletes the custom Helix work item expansion for debugger tests.
src/mono/wasm/debugger/Wasm.Debugger.Tests/Wasm.Debugger.Tests.csproj	Stops referencing the deleted Helix targets file.
src/mono/wasi/Makefile	Removes Helix build/submit targets for Wasm debugger tests.
src/libraries/tests.proj	Removes building the Wasm debugger test wrapper project as part of browser test traversal; updates sample-running condition.
src/libraries/sendtohelix.proj	Removes per-debugger-host project fan-out for the wasmdebuggertests scenario.
src/libraries/sendtohelix-wasm.targets	Removes the IsWasmDebuggerTests scenario marker property.
eng/pipelines/runtime.yml	Removes the Wasm debugger tests leg from the main runtime pipeline.
eng/pipelines/extra-platforms/runtime-extra-platforms-wasm.yml	Removes Wasm debugger test legs from extra-platform/wasm pipelines.
eng/pipelines/common/templates/wasm-debugger-tests.yml	Deletes the shared pipeline template used to run Wasm debugger tests.
eng/pipelines/common/evaluate-default-paths.yml	Removes the wasmdebuggertests path subset evaluation.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[akoeplinger]

/ba-g unrelated failures on Apple platforms