syz-fuzzer never exits (normally) so this does not affect syz-manager.
But during reproduction we can run a short running program (no repeat mode)
and currently VMs treat premature exit as an error.
Properly detect when a program exits and let callers decide what to do with it.
If an image supports all GCE fanciness, we don't need a separate ssh key for it.
It should accept the instance private key that we specify during VM creation.
VM.Close is called when syz-manager terminates on SIGINT.
Waiting for instance deletion in this case is unnecessary,
creation of a new instance will handle deleting instance.
So exit faster.
Log is a simple wrapper around std log package.
It is meant to solve 2 main problems:
1. Logging from non-main packages (mainly, vm/* packages).
Currently they can either always log or not log at all.
But they can't respect program verbosity setting.
Log package allows all packages to use the same verbosity setting.
2. Exposing recent logs in html UI.
Namely we want to tee logs to console and html UI.
