Add assertion race condition issue

[jmid]

This little PR adds the assertion race condition issue

[jmid]

CI summary:

• Win bytecode 5.1 timeout on threadomain [ocaml5-issue] Windows failures on threadomain #203
• Win 5.1 timeout on threadomain [ocaml5-issue] Windows failures on threadomain #203
  Out of 63 runs 2 workflows failed, both of which were genuine issues.

[jmid]

CI summary for merge to main:

• Linux 32bit 5.1 unexpectedly found a counterexample in Lin.Internal CList int test with Thread Lin.Internal Thread int CList test finds unexpected counterexample under bytecode #358
• Linux 5.1 debug triggered an assertion failure in thread_joingraph [ocaml5-issue] Abort / crash on thread_joingraph and thread_createtree under debug runtime #353
• Linux trunk debug triggered an assertion failure in threadomain [ocaml5-issue] Assertion failure on threadomain under debug runtime #404
• macos-arm64-5.0 unexpectedly found a counterexample in STM Sys test parallel STM parallel Sys tests on macOS #359
• freebsd-amd64-5.1 failed to find a counter example in 8418.0s Lin DSL Out_channel test with Domain(!) Lin Out_channel test fails to trigger on FreeBSD #401

Out of 38 workflows 5 failed, 2 were genuine failures and 3 were false alarms.