If posting an update resulted in an immediate error, don't communicate
this failure using the page flip feedback callbacks, but directly as a
return value.
This makes it possible for the direct client buffer scanout path not to
pass around flags triggering this behavior, meaning we can handle such
direct scanouts better.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
Custom page flips are meant to allow using e.g. EGLStream API to
indirectly trigger page flip queueing, when the KMS API cannot be used
directly. This is really something that is specific to a device, so
instead of making part of the page flip API, make it a configuration of
the update itself.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1488>
