Tests

Fix missing detection of dead code in expressions #21500

Job	Run time
Determine levels tests matrix	28s
Integration tests (windows-latest)	55s
Integration tests (ubuntu-latest)	45s
Tests (8.3, windows-latest)	1m 0s
Tests (8.2, ubuntu-latest)	41s
Tests (8.3, ubuntu-latest)	38s
Tests with old PHPUnit (7.4, ubuntu-latest)	1m 4s
Tests (8.4, windows-latest)	1m 3s
Tests with old PHPUnit (8.0, windows-latest)	56s
Tests with old PHPUnit (8.1, ubuntu-latest)	1m 4s
Tests (8.4, ubuntu-latest)	43s
Tests with old PHPUnit (7.4, windows-latest)	52s
Tests with old PHPUnit (8.1, windows-latest)	52s
Tests (8.2, windows-latest)	56s
Tests with old PHPUnit (8.0, ubuntu-latest)	1m 4s
Levels tests	-1s
	13m 0s

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