Try slipcover for coverage measurement on <= py3.11

[Zac-HD]

https://github.com/plasma-umass/slipcover - if the overhead of adding instrumentation is low, this could be a big win - and amortized across many unlikely-to-find-new-branches executions anyway if not. Note that we don't want to remove the instrumentation once hit, since we collect coverage for each test case.

[Zac-HD]

From Python 3.12, PEP-669, the sys.monitoring module offers a lower-overhead alternative to sys.settrace(). I'm planning to support that in HypothesisWorks/hypothesis#3773, and we should see if it makes sense to share code - or derive a variant if not.

[tybug]

As of 25.01.2, we now use sys.monitoring for coverage on 3.12+! Slipcover could still provide significant speedups for older versions, but is currently low priority as supporting another coverage-measurement interface would increase complexity.