Tests: Various harness improvements, especially on Windows #717

Job	Run time
code-quality / PHPCS	21s
code-quality / Lint PHP files	19s
code-quality / PHPStan	20s
code-quality / Lint Gherkin Feature files	20s
code-quality / Spell check	5s
code-quality / Lint GitHub Actions workflows	10s
	1m 35s

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