tox: run pytest with --durations flag to list tests run time

[dtrifiro]

By passing --durations, pytest reports the longest test run times.

Here's the top 5:

78.01s call     tests/model_management/test_tgis_auto_finder.py::test_bad_tgis_connection
4.23s call     tests/modules/text_generation/test_text_generation_tgis.py::test_local_train_load_tgis
3.31s call     tests/modules/text_generation/test_text_generation_local.py::test_train_model_save_and_load
1.86s call     tests/modules/text_generation/test_text_generation_local.py::test_train_model_seq2seq
1.75s call     tests/modules/text_generation/test_peft_prompt_tuning.py::test_run_model

It's probably worth it to add a timeout to test_bad_tgis_connection to avoid spending so much time there.

[evaline-ju]

LGTM! interesting how that one test can sometimes be fast or very slow