releng - investigate slipcover for coverage / or moving to python 3.12 (sys.monitoring)

[kapilt]

should significantly speed up the code coverage analysis in ci, which under normal load takes about 2.5x longer on runtime. we're not as effected because we also have a series of slow tests that are effectively masked by parallelism, so may not be as relevant.

alternatively we could fix up slow tests, but moving coverage to 3.12 for sys.monitoring is generally a good option.

[syed-awais-ali]

created a PR for the issue, please see #9529