Enable symplify/phpstan-rules 14.17 rule sets and fix reported errors

[TomasVotruba]

symplify/phpstan-rules 14.17.0 auto-loads all rule sets (naming, complexity, configurable, static, symfony, symfonyConfig, doctrine, phpunit). This keeps them all enabled and fixes the new errors:

• SniffFileProcessor::fixFile() - use $this->fixer instead of passing the service as an argument
• ECSConfig - set sniff properties via ReflectionProperty instead of a dynamic property name
• TurboRunner - FileSystem::delete() instead of @unlink()
• FileCacheStorage - drop @ on var_export(), errors are still caught via error_get_last()
• ParametersMerger - truthy check instead of empty()
• remove unused tests/functions.php dd() helper

Ignored in phpstan.neon by path:

• File::__construct() skips the parent constructor on purpose - it requires a PHP_CodeSniffer Ruleset ECS does not use
• static::class in AbstractSymplifyFixer::getName()
• property_exists() in TurboConfigDumper
• nullable StandaloneLineConstructorParamFixer in LineLengthFixer - hack to avoid running both rules together