This includes a qemu update from 8.2.2 to 9.2.1 which should hopefully
fix some bugs we have encountered.
PowerPC64LE is skipped for now because the new version seems to cause a
number of new SIGILLs.
Apply a handful of changes to reduce the diff between the two:
* Cancel running jobs on new pushes
* Enable log color and backtraces
* Add timeouts
* Specify CI runner versions
* Add an armv7 job
* Replace the name NO_STD with BUILD_ONLY
* Update the extension to the canonical .yaml
* Set AR_ and CC_ environments in docker
* Install requirements to build MPFR