ctf: make src.ctf.fs append error causes

ctf: make src.ctf.fs append error causes

This patch makes the src.ctf.fs plugin code append error causes whenever
an error status is returned.

A few new macros are added to comp-logging.h to support that.

Some functions are called both in component context and component class
context.  When appending error causes, we need to call the
function/macro for the right context.  My solution to this is to pass
both bt_self_component and bt_self_component_class pointers, but expect
only one of them to be set.  The new macro
BT_COMP_OR_COMP_CLASS_LOGE_APPEND_CAUSE takes care of calling the right
function for whichever is set.

Change-Id: I8d54f463d9a13066abdc140ef41f374e4daed303
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1966
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>