[wasm] test-main.js needs an unhandled exception handler #73330
Description
When running tests with xharness on browser, we are not able to get the traces for uncaught exceptions. A handler for that can print the trace which can be usable by anyone looking at test logs.
[11:20:03] info: Starting: System.Runtime.Tests.dll
[11:21:00] fail: [out of order message from the browser]: http://127.0.0.1:49197/dotnet.js 1880:6 Uncaught
[11:21:00] fail: [out of order message from the browser]: http://127.0.0.1:49197/dotnet.js 1880:6 Uncaught
[11:21:00] fail: [out of order message from the browser]: http://127.0.0.1:49197/dotnet.js 1880:6 Uncaught
[11:34:33] fail: Tests timed out. Killing driver service pid 7840
[11:34:33] fail: Application has finished with exit code TIMED_OUT but 0 was expected
Also, note the timings above. xharness continues to wait for 13mins after the uncaught exception, because the app did not signal that it had crashed.