Support pex3 cache prune --older-than ....

[jsirois]

Work towards #2528.

[jsirois]

Pants folks - this is FYI. It looks like Pants has not adopted Pex features in quite some time, but pex3 cache prune may be compelling. Unlike pex3 cache purge, it requires no knowledge of Pex internals and just does the right thing. The defaults (prune anything not used in the last 2 weeks) probably make sense to use as-is. If Pants had a cron job facility, this should probably be one of the canned cron jobs it ships with for example.

And clearly, the scie-jump should support the same technology, but that's for another time.

N.B.: As with pex3 cache purge, the prune will block for in-flight PEX runs / Pex CLI invocations to complete. This blocking is not super user-friendly out of the box, but is more so when psutil is installed. The released Pex PEX scies all have psutil included.

[huonw]

Thanks for the heads-up.