Tests: Various harness improvements, especially on Windows #715

Job	Run time
code-quality / Lint GitHub Actions workflows	8s
code-quality / PHPCS	22s
code-quality / Spell check	5s
code-quality / PHPStan	25s
code-quality / Lint Gherkin Feature files	15s
code-quality / Lint PHP files	14s
	1m 29s

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