Lua API: Unify server env checks and fix missing ones (#16457)

A few functions tried to dereference a ServerEnvironment nullptr by
calling 'getEnv()'. This change makes use of a macro where possible.

This also cleans up incorrect macro uses, with no functional difference.

src/script/lua_api/l_auth.cpp

@@ -15,14 +15,8 @@
 // common start: ensure auth db
 AuthDatabase *ModApiAuth::getAuthDb(lua_State *L)
 {
-	ServerEnvironment *server_environment =
-			dynamic_cast<ServerEnvironment *>(getEnv(L));
-	if (!server_environment) {
-		luaL_error(L, "Attempt to access an auth function but the auth"
-			" system is yet not initialized. This causes bugs.");
-		return nullptr;
-	}
-	return server_environment->getAuthDatabase();
+	GET_ENV_PTR_NO_MAP_LOCK;
+	return env->getAuthDatabase();
 }
 
 void ModApiAuth::pushAuthEntry(lua_State *L, const AuthEntry &authEntry)