Add bt_component_class_query_info() API

Add bt_component_class_query_info() API

When you create a component class, you can set an optional "query info"
class method with bt_component_class_sink_set_query_info_method().

A "query info" class method is a method which accepts an action name
and custom parameters and returns custom results. It can be used for
component class-specific requests such as getting the beginning and end
timestamps of a trace, its total size, and other statistics. On some
real-time source component class, it can be used to get a list of
endpoints to which to connect.

You can use bt_component_class_query_info() to query a component class.
The action name and parameters are mandatory, although you can use
bt_value_null for the parameters.

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