Refactor Orc JIT to enable lazy compilation (#974)

Refactor LLVM Orc JIT to actually enable the lazy compilation and speedup
the launching process:
  https://llvm.org/docs/ORCv2.html#laziness

Main modifications:
- Create LLVM module for each wasm function, wrap it with thread safe module
  so that the modules can be compiled parallelly
- Lookup function from aot module instance's func_ptrs but not directly call the
  function to decouple the module relationship
- Compile the function when it is first called and hasn't been compiled
- Create threads to pre-compile the WASM functions parallelly when loading
- Set Lazy JIT as default, update document and build/test scripts

core/shared/platform/windows/win_thread.c

@@ -164,7 +164,9 @@ static unsigned __stdcall os_thread_wrapper(void *arg)
     void *retval;
     bool result;
 
+#if 0
     os_printf("THREAD CREATED %p\n", thread_data);
+#endif
 
     os_mutex_lock(&parent->wait_lock);
     thread_data->thread_id = GetCurrentThreadId();