Add handling of `.skip_lint` file(s) #223

Job	Run time
Setup as in CI for tools (3.11)	3m 15s
Setup as in PR for tools (3.11)	42s
Test testing of tools (0, 3.11)	3m 57s
Test linting of tools (3.11)	37s
Test testing of tools (1, 3.11)	4m 10s
Test testing of tools (2, 3.11)	4m 16s
Test combining 'chunked' test results (3.11)	32s
	17m 29s

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