add option to dump backtrace of stop-the-world straggler (#57045)

[d-netto]

PR Description

Backports JuliaLang#57045.

I needed to make some minor adjustments in jl_gc_wait_for_the_world, because we're spinning waiting for the safepoint in 1.10, but we sleep on a condition in 1.12.

Marking as draft until I make the adjustments (e.g. pretty-printing the backtraces to JSON) to make sure this shows up on DD.

Checklist

Requirements for merging:

• I have opened an issue or PR upstream on JuliaLang/julia: add option to dump backtrace of stop-the-world straggler JuliaLang/julia#57045.
• I have removed the port-to-* labels that don't apply.
• I have opened a PR on raicode to test these changes:

[NHDaly]

Like we discussed, I think you should merge this as-is, and then make any other changes in a separate commit, so that we can separate the backport and the RAI-specific changes we'd want to keep.

[d-netto]

Ran the MWE with julia -t4 --timeout-for-safepoint-straggler=1:

function main()
    t = Threads.@spawn begin
        ccall(:uv_sleep, Cvoid, (Cuint,), 5000)
    end
    # Force a GC
    ccall(:uv_sleep, Cvoid, (Cuint,), 1000)
    GC.gc()
    wait(t)
end
main()

And got:

===== Thread 4 failed to reach safepoint after 1 seconds, printing backtrace below =====
thread (1) __semwait_signal at /usr/lib/system/libsystem_kernel.dylib (unknown line)
===== Thread 4 failed to reach safepoint after 1 seconds, printing backtrace below =====
thread (1) __semwait_signal at /usr/lib/system/libsystem_kernel.dylib (unknown line)
===== Thread 4 failed to reach safepoint after 1 seconds, printing backtrace below =====
thread (1) __semwait_signal at /usr/lib/system/libsystem_kernel.dylib (unknown line)