In this PR, we update the LocalBackend so that when the ReconnectAfter policy setting is configured
and a user disconnects Tailscale by setting WantRunning to false in the profile prefs, the LocalBackend
will now start a timer to set WantRunning back to true once the ReconnectAfter timer expires.
We also update the ADMX/ADML policy definitions to allow configuring this policy setting for Windows
via Group Policy and Intune.
Updates #14824
Signed-off-by: Nick Khyl <nickk@tailscale.com>