lib: remove "accept port" concept

lib: remove "accept port" concept

This patch removes the concept of a component needing to accept a port
connection before a connection is made.  Since the component connections
are supposed to be transparent (a component behavior shouldn't change
based on which component is on the other side), there is no point in
letting a component refuse a connection.  Refusing a port connection
based on the component class, for example, could lead to tightly coupled
components, which we want to avoid.

Change-Id: Ia2d0e09caaee069e9be22b8089ef5ccbae392bb2
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1522
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>