src/cpp-common/bt2: wrap dynamic array with length field loc. FC API

src/cpp-common/bt2: wrap dynamic array with length field loc. FC API

This patch adds what's needed to the C++ libbabeltrace2 wrappers to
wrap:

* bt_field_class_array_dynamic_with_length_field_borrow_length_field_location_const()
* bt_field_class_array_dynamic_without_length_field_location_create()
* bt_field_class_array_dynamic_with_length_field_location_create()

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Change-Id: I7d731807165e22de9ec97d9cd83ec75e02c759b1
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8017
Reviewed-on: https://review.lttng.org/c/babeltrace/+/12700
Tested-by: jenkins <jenkins@lttng.org>
CI-Build: Simon Marchi <simon.marchi@efficios.com>