Test Failures With Thread Sanitizer

[insertinterestingnamehere]

Again, unclear to what extent these are actual failures vs just needing some additional work to enable thread sanitizer, however all the following fail with thread sanitizer enabled on clang 17.

arbitrary_blocking_operation
external_fork
external_syncvar
qthread_fork_precond
qthread_migrate_to
qthread_disable_shepherd

Possibly related: #145.

[insertinterestingnamehere]

I'm working through these errors now and they're proving to be detailed enough that it's worthwhile to triage/document them individually. I'll leave this main issue for thread sanitizer errors open and link the individual issues here.