Add coverage and number of reproducing programs to the periodic messages.
When all machines are busy reproducing crashes, it appears that
syz-manager hanged as number of executed programs does not increase.
Coverage is just a nice characteristic.
Also print machine check message, it appears once and contains useful info.
Add a new isolated VM for machines that you cannot easily manage. It
assumes the machine is only available through SSH and create a reverse
proxy to ensure the machine can connect back to syz-manager.
Signed-off-by: Thomas Garnier <thgarnie@google.com>
