Add ConfigVAlpha.RemoteConfig so a user-data/cloud-init config can
delegate remote control to the tailnet admin (see Prefs.RemoteConfig).
Updates #1866
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
One AMI now self-configures from user-data or, when absent, enrolls over
serial.
Updates #1866
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>