Coverage: Implement fail_under #2308

Job	Run time
Run tests (3.9)	8s
Run tests (3.10.4)	18s
Run tests (3.11)	10s
Run tests (3.11.0)	19s
Run tests (3.10)	16s
Run tests (3.12)	12s
Run tests (3.9.12)	22s
Run tests (pypy3.9)	12s
Run tests (pypy3.10)	12s
Run tests (3.13.0)	15s
Run tests (3.14)	17s
Run tests (3.13)	12s
Run tests (pypy3.11)	10s
Run tests (3.12.0)	16s
Report coverage	14s
Create an issue if daily tests failed	0s
	3m 33s

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