tests/lib/conds/test.py: use `tjson`, add type annotations

tests/lib/conds/test.py: use `tjson`, add type annotations

Use `tests/utils/python/tjson.py` and add some types annotations to make
`tests/lib/conds/test.py` pyright-clean:

    $ PYTHONPATH=/home/simark/src/babeltrace/tests/utils/python pyright tests/lib/conds/test.py
    0 errors, 0 warnings, 0 informations

Change-Id: Ie7e233e51b5fef645f6ca2c23a66e8c81f00f2a8
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/11780
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>