[wasm] Re-enable ~6700 runtime tests that got disabled mistakenly (#86747)

[wasm] Re-enable ~6700 runtime tests that got disabled mistakenly (#86747)

* [wasm] Fix running merged test wrappers in runtime tests

- These were all getting removed because it looked for the incorrect
  script path in case of wasm

* [wasm] Disable a multithreaded runtime test

```
Operation is not supported on this platform.
   at System.Threading.Thread.ThrowIfNoThreadStart(Boolean internalThread)
   at System.Threading.Thread.Start(Boolean captureContext, Boolean internalThread)
   at System.Threading.Thread.Start()
   at MutualThdRecur_fptr.main()
   at Program.<>c__DisplayClass0_0.<<Main>$>g__TestExecutor29|30(TestFilter filter, StreamWriter tempLogSw, StreamWriter statsCsvSw)
```

* [wasm] Disable a failing test in JIT.Performance

`JIT/Performance/CodeQuality/Benchstones/MDBenchI/MDPuzzle/`
https://github.com/dotnet/runtime/issues/86772

* [wasm] Disable all JIT.Performance tests for now