rr chaos mode for stress testing garbage collection

[MilesCranmer]

x-post from #520 (comment). Probably useful for when #529 lands.

Regarding testing, it could be nice to try something like rr's chaos mode to assault the garbage collector in multithreaded mode and reveal any potential thread safety issues.

It is tricky to start Julia with rr from within Python – see JuliaLang/julia#52689. So the test would have to be run from the Julia side of PythonCall.jl, and open Python from there, rather than the other direction. But maybe that would be good enough for testing this.

I believe the Julia version of this can be done with

julia --bug-report=rr-local,chaos

which starts a new Julia process using BugReporting.jl.

BugReporting.jl looks to launch rr using

https://github.com/JuliaLang/BugReporting.jl/blob/fec2ece8be317462fe8b93ffca56e5b228d0b341/src/BugReporting.jl#L162

    rr_cmd = `$(rr()) record $rr_flags $julia_cmd $julia_args`

where rr_flags contains --chaos for chaos mode.

So perhaps the BugReporting.jl package could be installed for testing, which automatically installs rr. This could be used for referencing the rr executable with BugReporting.rr().

cc @ericphanson