Use pre-created exec_env for instantiation and module_malloc/free (#2047)

Use pre-created exec_env for instantiation and module_malloc/free,
use the same exec_env of the current thread to avoid potential
unexpected behavior.

And remove unnecessary shared_mem_lock in wasm_module_free,
which may cause dead lock.

core/iwasm/libraries/lib-pthread/lib_pthread_wrapper.c

@@ -581,7 +581,7 @@ pthread_create_wrapper(wasm_exec_env_t exec_env,
 #endif
 
     if (!(new_module_inst = wasm_runtime_instantiate_internal(
-              module, true, stack_size, 0, NULL, 0)))
+              module, true, exec_env, stack_size, 0, NULL, 0)))
         return -1;
 
     /* Set custom_data to new module instance */