The backend is not able to tell whether a surface is being
presented via direct scan-out or not. The backend will set
ZERO_COPY if the buffer submitted via the output commit was
presented in a zero-copy fashion, but will no know whether the
buffer comes from the compositor or the client.
Using "present" is confusing here: the event is emitted when the
buffer is being sampled to be displayed on an output, not when it's
being presented on-screen.
Rename to match the presentation-time terminology.