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)
```
Support collecting code coverage with wamr-test-suites script by using
lcov and genhtml tools, eg.:
cd tests/wamr-test-suites
./test_wamr.sh -s spec -b -P -C
The default code coverage and html files are generated at:
tests/wamr-test-suites/workspace/wamr.lcov
tests/wamr-test-suites/workspace/wamr-lcov.zip
And update wamr-test-suites scripts to support testing GC spec cases to
avoid frequent synchronization conflicts between branch main and dev/gc.
This syscall doesn't need allocating stack or TLS and it's expected from the application
to do that instead. E.g. WASI-libc already does this for `pthread_create`.
Also fix some of the examples to allocate memory for stack and not use stack before
the stack pointer is set to a correct value.
