chore: enable -Wextra compiler flag and suppress unused-parameter warnings

Enable the -Wextra compiler flag in the wren.mk build configuration, which was previously commented out with a TODO. To handle the new unused parameter warnings triggered by -Wextra (particularly for WrenVM* vm parameters in several functions), add -Wno-unused-parameter to suppress them. Also fix a declaration ordering issue in wren_vm.c where the 'static' keyword was placed after the return type in loadIntoCore, moving it to the correct position before the type specifier.

src/vm/wren_vm.c

@@ -1363,7 +1363,7 @@ void wrenReleaseMethod(WrenVM* vm, WrenMethod* method)
 }
 
 // Execute [source] in the context of the core module.
-WrenInterpretResult static loadIntoCore(WrenVM* vm, const char* source)
+static WrenInterpretResult loadIntoCore(WrenVM* vm, const char* source)
 {
   ObjModule* coreModule = getCoreModule(vm);