feat(hack): add scripts to drive the dev environment headless

Start QEMU in the background with a QMP socket and console logs, take
screenshots, press keys and wait for serial output, so the graphical boot
menu can be driven without a terminal or a window. boot.sh gets opt-in
knobs for this and behaves as before otherwise.

hack/dev/run/status.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+# Prints the state of QEMU: stopped, or the pid and the VM status such as running.
+# Exits 1 when QEMU isn't running.
+set -e
+
+cd "$(dirname "${0}")/../../.." || exit 1
+
+. "hack/dev/run/lib.sh"
+
+if ! is_running; then
+	echo "stopped"
+	exit 1
+fi
+
+echo "pid $(cat "${PID_FILE}") $(./hack/dev/run/qmp.sh '{"execute":"query-status"}' 2>/dev/null || echo "no qmp")"