sink.text.details: handle field classes with field locations

sink.text.details: handle field classes with field locations

Handle MIP 1 variant, option and dynamic array field classes.  They
have field locations instead of field paths.

The format used by write_field_location is based on write_field_path.

Change-Id: Ic2f6e1ed233a34ea4cc647f50eaf4027b9e5bff8
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/7500
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/12691