tests: declare the Lua engine for the LuaLibrary tests

Scribunto 1.46 requires each LuaEngineTestBase subclass to declare its engine
via getEngineName(); the previous "one class exercises every engine"
data-provider pattern is deprecated. Without it the LuaLibrary tests error on
1.46+ with "must implement getEngineName()". Target LuaStandalone, whose
interpreter Scribunto bundles, so the tests run in CI without installing a Lua
extension.

Pre-1.46 MediaWiki does not call getEngineName() (it runs every configured
engine through its own suite() machinery), so the method is inert there: the
REL1_43 to REL1_45 rows are unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: malberts

tests/phpunit/Unit/LuaLibraryTestBase.php

@@ -22,6 +22,10 @@ abstract class LuaLibraryTestBase extends LuaEngineTestBase
 	 */
 	private $luaLibrary;
 
+	protected function getEngineName(): string {
+		return 'LuaStandalone';
+	}
+
 	/**
 	 * @throws RuntimeException
 	 */