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

samples/terminate/src/main.c

@@ -39,7 +39,7 @@ runner_with_spawn_exec_env(void *vp)
     wasm_function_inst_t func;
     bool ok = wasm_runtime_init_thread_env();
     assert(ok);
-    func = wasm_runtime_lookup_function(inst, "block_forever", NULL);
+    func = wasm_runtime_lookup_function(inst, "block_forever");
     assert(func != NULL);
     wasm_runtime_call_wasm(env, func, 0, NULL);
     wasm_runtime_destroy_spawned_exec_env(env);