UB-free `analysis/test` WIP

[kkysen]

All UB in analysis/test should be gone according to miri. Now I can't reproduce the failures locally. Let's see about CI.

[kkysen]

Well, this is still failing CI, welp.

Some ideas for investigating further that we discussed:

• Trying to replicate the CI environment locally as much as possible, like running with reduced core count and under heavy load.
• Check to see if rustc and our instrumentation is being deterministic.
• Check to see if any events are being lost. Perhaps try processing the events on the main thread to keep things single-threaded, as perhaps there's a bug in there, especially around finalization when the main thread finishes first.
• See if rr could be used to debug post-mortem.

[oinoom]

What's the high level difference between this and #683 ?

[kkysen]

What's the high level difference between this and #683 ?

This PR is just everything thrown together in 1 commit. There might be some other changes added in here, too.

Also, #683 only fixes the UB. Other PRs fix the rest of the things in here.

[kkysen]

Closing as this was a WIP and is now complete in:

• #653
• #683
• #684
• #686
• #698