[wasm] Add Wasm.Debugger.Tests wrapper project  …
This is a proxy/wrapper project for `src/mono/wasm/debugger/DebuggerTestSuite/DebuggerTestSuite.csproj`.

- Building the project as part of the regular browser-wasm build
  presents some issues, because of part the tests need use the aspnet
  sdk, and that doesn't work with `browser-wasm`.
- This wrapper project essentially builds the `DebuggerTestSuite`
  project, with some
  properties(`TargetFramework;TargetFrameworks;Configuration;TargetOS;TargetArchitecture`)
  removed so they don't propogate from the parent build.
  - And it packages it up for running the tests on helix

- I did try to convert `DebuggerTestSuite` into a `Wasm.Debugger.Tests`,
  and make it use the library tests infrastructure, but ran into an
  issue
  - it built the project with no `testhost.dll`, so can't use `dotnet
    test`
  - it did get `xunit.console.dll`, but that would fail to run the tests
    because of missing `System.Runtime` (and I'm guessing, other
    assemblies)
    - attempts to publish the project failed
    - So, for now, this is what we have!```

IIUC, the test discoverers are not being run with this, which means that we can't use `ActiveIssue`, and other similar attributes. As a workaround, it uses `windows-failing`, and `linux-failing` traits.