Don't reset non replayed timestamps

Quoting the last commit:

    x11: Limit touch replay pointer events to when replaying
    
    When a touch sequence was rejected, the emulated pointer events would be
    replayed with old timestamps. This caused issues with grabs as they
    would be ignored due to being too old. This was mitigated by making sure
    device event timestamps never travelled back in time by tempering with
    any event that had a timestamp seemingly in the past.
    
    This failed when the most recent timestamp that had been received were
    much older than the timestamp of the new event. This could for example
    happen when a session was left not interacted with for 40+ days or so;
    when interacted with again, as any new timestamp would according to
    XSERVER_TIME_IS_BEFORE() still be in the past compared to the "most
    recent" one. The effect is that we'd always use the `latest_evtime` for
    all new device events without ever updating it.
    
    The end result of this was that passive grabs would become active when
    interacted with, but would then newer be released, as the timestamps to
    XIAllowEvents() would out of date, resulting in the desktop effectively
    freezing, as the Shell would have an active pointer grab.
    
    To avoid the situation where we get stuck with an old `latest_evtime`
    timestamp, limit the tempering with device event timestamp to 1) only
    pointer events, and 2) only during the replay sequence. The second part
    is implemented by sending an asynchronous message via the X server after
    rejecting a touch sequence, only potentially tempering with the device
    event timestamps until the reply. This should avoid the stuck timestamp
    as in those situations, we'll always have a relatively up to date
    `latest_evtime` meaning XSERVER_TIME_IS_BEFORE() will not get confused.