[dx] warn about deprecated beforeTraverse() method once FileNode is ready #31823

Job	Run time
PHPStan	1m 32s
Help and Version	23s
Composer Validate	21s
Preload php-parser Order	21s
Commented Code	22s
Check no "*.php" files in rules Fixture directory	22s
Run with Space in Directory	27s
Compatible PHPStan versions	19s
Active Classes	27s
Detect composer dependency issues	22s
PHP Linter	29s
Finalize classes	22s
Check fixture classes are different to nodes	21s
Check before/after test fixture on no-changes	19s
	6m 27s

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