This moves about 2/3rds of the code from `firezone-gui-client` to
`firezone-gui-client-common`.
I tested it in aarch64 Windows and cycled through sign-in and sign-out
and closing and re-opening the GUI process while the IPC service stays
running. IPC and updates each get their own MPSC channel in this, so I
wanted to be sure it didn't break.
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Signed-off-by: Reactor Scram <ReactorScram@users.noreply.github.com>
Co-authored-by: Thomas Eizinger <thomas@eizinger.io>
