[Feature request] acceptance test class to run user-mode binaries

This bug has been copied automatically from: https://bugs.launchpad.net/qemu/+bug/1874674

Currently the acceptance test framework only target system-mode emulation.
It would be useful to test user-mode too.

Ref: https://www.mail-archive.com/qemu-devel@nongnu.org/msg626610.html