Add handling of `.skip_lint` file(s) #226

Job	Run time
Setup as in CI for tools (3.11)	3m 18s
Setup as in PR for tools (3.11)	41s
Test linting of tools (3.11)	32s
Test testing of tools (0, 3.11)	3m 28s
Test testing of tools (1, 3.11)	3m 34s
Test testing of tools (2, 3.11)	3m 54s
Test combining 'chunked' test results (3.11)	38s
	16m 5s

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