Since the last commit, we have infrastructure in place in the ScreencastService
to blocklist pipelines which crashed the recorder.
If such a crash happens a few minutes into a screencast, we can't do any better
than telling the user about the problem and encouraging them to try again (with
the faulty pipeline now blocklisted).
If the crash happens while starting the recording though, we can actually do
better: We can try to auto-restart the ScreencastService ourselves, and the
recording might still succeed without the user noticing anything. So retry
that start of the recorder for two more times, and then finally give up.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2976>
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