ci: add environment var for table issue on MacOS

This commit tries to fix some flakiness of the test execution over MacOS-based instances over GitHub Actions.

It appears to be an issue of the `tables` dependency. From the logs of the CI: (https://github.com/bancaditalia/black-it/actions/runs/7121188681/job/19389914846?pr=78#step:5:62)

```
Fatal Python error: Illegal instruction

Current thread 0x000000011783c600 (most recent call first):
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/tables/node.py", line 246 in __init__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/tables/leaf.py", line 264 in __init__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/tables/carray.py", line 200 in __init__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/tables/earray.py", line 143 in __init__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/tables/file.py", line 1345 in create_earray
  File "/Users/runner/work/black-it/black-it/black_it/utils/json_pandas_checkpointing.py", line 211 in save_calibrator_state
  File "/Users/runner/work/black-it/black-it/tests/test_utils/test_pandas_json_checkpointing.py", line 58 in test_save_and_load_calibrator_state
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/python.py", line 194 in pytest_pyfunc_call
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_callers.py", line 77 in _multicall
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_manager.py", line 115 in _hookexec
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_hooks.py", line 493 in __call__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/python.py", line 1792 in runtest
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/runner.py", line 169 in pytest_runtest_call
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_callers.py", line 77 in _multicall
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_manager.py", line 115 in _hookexec
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_hooks.py", line 493 in __call__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/runner.py", line 262 in <lambda>
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/runner.py", line 341 in from_call
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/runner.py", line 261 in call_runtest_hook
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/runner.py", line 222 in call_and_report
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/runner.py", line 133 in runtestprotocol
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/runner.py", line 114 in pytest_runtest_protocol
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_callers.py", line 77 in _multicall
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_manager.py", line 115 in _hookexec
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_hooks.py", line 493 in __call__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/main.py", line 350 in pytest_runtestloop
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_callers.py", line 77 in _multicall
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_manager.py", line 115 in _hookexec
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_hooks.py", line 493 in __call__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/main.py", line 325 in _main
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/main.py", line 271 in wrap_session
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/main.py", line 318 in pytest_cmdline_main
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_callers.py", line 77 in _multicall
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_manager.py", line 115 in _hookexec
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/pluggy/_hooks.py", line 493 in __call__
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/config/__init__.py", line 169 in main
  File "/Users/runner/work/black-it/black-it/.tox/py310/lib/python3.10/site-packages/_pytest/config/__init__.py", line 192 in console_main
  File "/Users/runner/work/black-it/black-it/.tox/py310/bin/pytest", line 8 in <module>
```

The solution as suggested by https://stackoverflow.com/a/73030329 and 9cb07d0, was to set certain variables to the environment.

.github/workflows/test.yml

@@ -37,6 +37,11 @@ jobs:
 #      env:
 #        ACTIONS_ALLOW_UNSECURE_COMMANDS: true
 #      run: ...
+    - if: matrix.os == 'macos-latest'
+      name: Set up MacOS variables
+      run: |
+        echo "HDF5_DIR=/opt/homebrew/opt/hdf5" >> $GITHUB_ENV 
+        echo "BLOSC_DIR=/opt/homebrew/opt/c-blosc" >> $GITHUB_ENV
     - if: ${{ (matrix.os == 'ubuntu-latest') || (matrix.os == 'macos-latest') }}
       name: Unit tests and coverage (ubuntu-latest, macos-latest)
       run: |