PSA: Dispatching background tasks just got easier!

Hello! Now that Bug 1584568 just landed I wanted to mention the new background thread pool for general purpose and blocking IO runnables. Existing one-off threads, as well as new jobs that you may want to run async in the background, can go to the new background thread

PSA: Hang Reports in tests now have the correct crash signature

[Cross-posting to stability] In tests, the crash report now correctly reflects the hanging or crashing process. With Bug 1605328 fixed, the crashing process .dmp file will be sorted at the top of the list and therefore output the hanging