Tests: Various harness improvements, especially on Windows #716

Job	Run time
code-quality / Lint PHP files	22s
code-quality / Spell check	5s
code-quality / PHPStan	27s
code-quality / Lint Gherkin Feature files	16s
code-quality / PHPCS	20s
code-quality / Lint GitHub Actions workflows	9s
	1m 39s

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