* Improve OOB hook
This moves the hook to be executed outside of busy loop
considering the thread to be truly idle at a time of execution
of the hook
* Further improvements to out-of-band hook
* Don't trigger OOB on partially-queued requests
* Don't accept new connections during OOB
* Move tests to `TestOutOfBandServer`
Co-authored-by: Kamil Trzcinski <ayufan@ayufan.eu>
Co-authored-by: Nate Berkopec <nate.berkopec@gmail.com>
