Investigate moving other packages in ./scripts to ./python

There are a few other python packages in ./scripts that are imported and used by other scripts that suggests they might benefit from a stricter regression testing regime.

Assuming that moving ./scripts/qmp (jsnow/qemu#13 (moved), jsnow/qemu#17 (moved)) and ./scripts/qapi (jsnow/qemu#9 (moved)) goes well, investigate a few other likely culprits; these all have some dependency on qemu.qmp and/or qemu.machine.

device-crash-test:from qemu.machine import QEMUMachine
render_block_graph.py:from qemu.qmp import (
simplebench/bench_block_job.py:from qemu.machine import QEMUMachine
simplebench/bench_block_job.py:from qemu.qmp import QMPConnectError

• device-crash-test is a likely culprit for qemu.utils
• render_block_graph is a likely culprit for an optional, extended functionality available via qmp-shell
• simplebench is a likely culprit for an entirely new subpackage for qemu.