Introduce FileNode to handle file-level changes #31807

Job	Run time
Help and Version	21s
Finalize classes	32s
Composer Validate	19s
Preload php-parser Order	24s
Run with Space in Directory	23s
Compatible PHPStan versions	20s
Active Classes	26s
Commented Code	22s
PHPStan	1m 32s
Check no "*.php" files in rules Fixture directory	19s
Check fixture classes are different to nodes	17s
Detect composer dependency issues	17s
Check before/after test fixture on no-changes	19s
PHP Linter	33s
	6m 24s

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