Add test data from str samples and speed up tests

[endast]

What

This PR does 5 things:

• Speeds up the deeprvat tests by using pytest-xdist to run the tests in parallel:

  Before (on Apple M2 MacBook Pro):

(deeprvat_non_cuda) *[feature/tests-optimize][~/code/deeprvat]$ pytest tests/deeprvat     
=== test session starts ===
platform darwin -- Python 3.8.15, pytest-8.1.1, pluggy-1.4.0
rootdir: /Users/b260-admin/code/dkfz/deeprvat
plugins: xdist-3.5.0
collected 9 items                                                                                                                                                                                                                                                                                                      

tests/deeprvat/test_train.py .........                                                          [100%]

pytest tests/deeprvat
============================= 9 passed, 26 warnings in 251.47s (0:04:11) =============================

After

(deeprvat_non_cuda) *[feature/tests-optimize][~/code/deeprvat]$ pytest -n auto tests/deeprvat
========================================= test session starts =========================================
platform darwin -- Python 3.8.15, pytest-8.1.1, pluggy-1.4.0
rootdir: /Users/b260-admin/code/dkfz/deeprvat
plugins: xdist-3.5.0
12 workers [9 items]      
.........                                                                                                                                                                                                                                                                                                        [100%]
============================= 9 passed, 48 warnings in 74.11s (0:01:14)=============================

• Updates pytest to 8.2.0
• Adds non integer samples to the test data. The first sample in the h5 got SAM prepended SAM0 in the preprocessing sample vcfs the first to samples were changed to S10000001 and S10000002
• Changes so we don't cast samples to int when passing them to get_matched_sample_indices.
• Fixes so the deeprvat tests can be started from any folder (not just repo root), by setting the workdir in the test.
• Locks down ubuntu images to 24.04

Testing

Test running the sample pipelines and the test to make sure they pass and that the data is in the expected format.

Related issue:

https://github.com/PMBio/deeprvat/issues/70