Update wasi-libc version to resolve the hang issue when running wasi-threads cases.
Implement custom sync primitives as a counterpart of `pthread_barrier_wait` to
attempt to replace pthread sync primitives since they seem to cause data races
when running with the thread sanitizer.
`wasi-sdk-20` pre-release can be used to avoid building `wasi-libc` to enable threads.
It's not possible to use `wasi-sdk-20` pre-release on Ubuntu 20.04 because of
incompatibility with the glibc version:
```bash
/opt/wasi-sdk/bin/clang: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found
(required by /opt/wasi-sdk/bin/clang)
```
Raising "wasi proc exit" exception, spreading it to other threads and then
clearing it in all threads may result in unexpected behavior: the sub thread
may end first, handle the "wasi proc exit" exception and clear exceptions
of other threads, including the main thread. And when main thread's
exception is cleared, it may continue to run and throw "unreachable"
exception. This also leads to some assertion failed.
Ignore exception spreading for "wasi proc exit" and don't clear exception
of other threads to resolve the issue.
And add suspend flag check after atomic wait since the atomic wait may
be notified by other thread when exception occurs.
