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/aot/aot_runtime.h

@@ -499,14 +499,12 @@ aot_deinstantiate(AOTModuleInstance *module_inst, bool is_sub_inst);
  *
  * @param module_inst the module instance
  * @param name the name of the function
- * @param signature the signature of the function, use "i32"/"i64"/"f32"/"f64"
- *        to represent the type of i32/i64/f32/f64, e.g. "(i32i64)" "(i32)f32"
  *
  * @return the function instance found
  */
 AOTFunctionInstance *
-aot_lookup_function(const AOTModuleInstance *module_inst, const char *name,
-                    const char *signature);
+aot_lookup_function(const AOTModuleInstance *module_inst, const char *name);
+
 /**
  * Call the given AOT function of a AOT module instance with
  * arguments.