Resurrect `V8` engine

[marxin]

The back end was paused for a while, and there may be several gaps we still need to address.

• Module serialization/deserialization (unless --disable-cache is used) is borked: (apparently also related to the threading limitation)

#0  0x00007ffff7d8600d in ?? () from /usr/lib/libc.so.6
#1  0x000055555a630b9d in v8::internal::wasm::WasmSerializer::SerializeNativeModule(v8::base::Vector<unsigned char>) const ()
#2  0x00005555599e3393 in wasm::Module::serialize() const ()
#3  0x00005555599e862f in wee8_wasm_module_serialize ()
#4  0x000055555996fd09 in wasmer::backend::v8::entities::module::ModuleHandle::serialize (self=0x7fff84094040) at lib/api/src/backend/v8/entities/module.rs:116

• pthread_create does not succeed -> given the per-thread Store requirement I don't see the full picture yet. Thoughts on that?

• fork functionality not properly covering both of the processes:

fork.c.txt

Parent: PID = 1, Child PID = 2

• Apparently, the V8's downstream patch about shareable memory might be not working correctly. For a pthread_create test-case, I face: WARN ThreadId(29) wasmer_wasix::runtime::task_manager: could not clone memory error=The memory is invalid because memory is not a shared memory type (fix(Memory): properly preserve shared attribute of a Memory v8-custom-builds#5) (tests(V8): shareable memory with V8, bump V8 release #6544).

[marxin]

Seems the original issue can be mitigated with --disable-cache, however, anything non-trivial does not work either:

thread 'TokioTaskManager Thread Pool_thread_1' (3127254) panicked at lib/api/src/backend/v8/entities/mod.rs:18:9:
Fatal error (v8): current thread is different from the thread the store was created in!
stack backtrace:

[Arshia001]

@marxin one more thing we probably don't have yet is support for the async runtime and Function::call_async*. This is necessary for WASIX to run properly, and will impact running Python codebases.

Also, let's please make sure we have a proper implementation around exception references; imported functions should be able to raise an exception by returning Err(RuntimeError::exception(...)) and embedders should be able to both construct and catch exceptions.