Convert all classes to strict variable types

All variable declarations in all classes have a strict type set

Exception: constants (will be setable from PHP 8.3 on), resources (no type)

Debug\LoggingLegacy is kept as is, will be deprecated

www/lib/CoreLibs/Check/Encoding.php

@@ -11,7 +11,7 @@ namespace CoreLibs\Check;
 class Encoding
 {
 	/** @var int<min, -1>|int<1, max>|string */
-	private static $mb_error_char = '';
+	private static int|string $mb_error_char = '';
 
 	/**
 	 * set error char