Remove unused argument in wasm_runtime_lookup_function and refactor WASMModuleInstance (#3218)

Remove the unused parameter `signature` from `wasm_runtime_lookup_function`.

Refactor the layout of WASMModuleInstance structure:
- move common data members `c_api_func_imports` and `cur_exec_env` from
  `WASMModuleInstanceExtraCommon` to `WASMModuleInstance`
- In `WASMModuleInstance`, enlarge `reserved[3]` to `reserved[5]` in case that
  we need to add more fields in the future

ps.
https://github.com/bytecodealliance/wasm-micro-runtime/issues/2530
https://github.com/bytecodealliance/wasm-micro-runtime/issues/3202

core/iwasm/libraries/lib-wasi-threads/lib_wasi_threads_wrapper.c

@@ -98,8 +98,8 @@ thread_spawn_wrapper(wasm_exec_env_t exec_env, uint32 start_arg)
 
     wasm_native_inherit_contexts(new_module_inst, module_inst);
 
-    start_func = wasm_runtime_lookup_function(new_module_inst,
-                                              THREAD_START_FUNCTION, NULL);
+    start_func =
+        wasm_runtime_lookup_function(new_module_inst, THREAD_START_FUNCTION);
     if (!start_func) {
         LOG_ERROR("Failed to find thread start function %s",
                   THREAD_START_FUNCTION);