tests/lib: C++ify `conds/conds-triggers.cpp`

tests/lib: C++ify `conds/conds-triggers.cpp`

 - use an anonymous namespace for local stuff
 - use bt2 C++ bindings
 - rename functions to camel case
 - mark functions as `noexcept`

Change-Id: Id31e3703eb48662cc3090d57247fb16bcea0d7f8
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/11797
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>