ctf: notif-iter: pass current stream ID to get_stream() medop

ctf: notif-iter: pass current stream ID to get_stream() medop

Make the notif iter's get_stream() medop receive the current stream
(instance) ID as a parameter, if any, so that the callee can create a
stream with bt_ctf_stream_create_with_id(), if this is needed, with the
appropriate stream ID which is only known dynamically after decoding the
first packet header.

In the case of src.ctf.fs, the streams are already created with the
appropriate stream IDs because the component deals with data stream file
groups and must mark the trace as static at creation time, so the new
parameter is ignored. In the case of src.ctf.lttng-live, we cannot read
the first packet header and then rewind (or it is rather complicated to
do so), so the stream object is created the first time get_stream() is
called with the received ID.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>