ir: add stream ID API

ir: add stream ID API

The new bt_ctf_stream_create_with_id() function creates a stream object,
just like bt_ctf_stream_create(), but with a numeric ID. You cannot
call this function to create a CTF writer stream because CTF writer
streams initialize their own unique ID.

Use bt_ctf_stream_get_id() to get a stream's ID.

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