Add handling of `.skip_lint` file(s) #222

Job	Run time
Setup as in PR for tools (3.11)	56s
Setup as in CI for tools (3.11)	3m 56s
Test linting of tools (3.11)	40s
Test testing of tools (0, 3.11)	5m 11s
Test testing of tools (1, 3.11)	3m 29s
Test testing of tools (2, 3.11)	4m 41s
Test combining 'chunked' test results (3.11)	43s
	19m 36s

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