ctf: make ctf_trace_class_configure_ir_trace use bt2::Trace

ctf: make ctf_trace_class_configure_ir_trace use bt2::Trace

Use the bt2::Trace wrapper instead of a raw `bt_trace *`.  Change the
return type to void, since failures are now reported using exceptions.

Change-Id: I2e30b0aa9a6f33e765ac32d274032ef4ab3aa9f8
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8417
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>