Similar to de30de865cd, this allows to follow the flow of events as they
arrive to a pad rather than only when they are pushed to a peer.
The hook is installed in gst_pad_send_event_unchecked() instead of
gst_pad_send_event() because the latter is often omitted: that is the
case especifically in gst_pad_push_event_unchecked(), where most event
propagation occurs.
This patch also makes use of the new hooks in the log tracer to log the
begining and end of the send_event processing.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8330>
Instead of having each tracer implement its own parameter parsing,
centralize the handling in the tracer subsystem using GstStructure.
This simplifies tracer implementations and provides a consistent way
to handle properties.
It also allows for much better documentation by forcing tracer object
to expose properties
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8086>
