pvf: Log memory metrics from preparation (#6565)

* Add getrusage and memory tracker for precheck preparation

* Log memory stats metrics after prechecking

* Fix tests

* Try to fix errors (linux-only so I'm relying on CI here)

* Try to fix CI

* Add module docs for `prepare/memory_stats.rs`; fix CI error

* Report memory stats for all preparation jobs

* Use `RUSAGE_SELF` instead of `RUSAGE_THREAD`

Not sure why I did that -- was a brainfart on my end.

* Revert last commit (RUSAGE_THREAD is correct)

* Use exponential buckets

* Use `RUSAGE_SELF` for `getrusage`; enable `max_rss` metric for MacOS

* Increase poll interval

* Revert "Use `RUSAGE_SELF` for `getrusage`; enable `max_rss` metric for MacOS"

This reverts commit becf7a815409ab530fc61370abffcd1b97b9a777.