Add environment variable AMICI_DLL_DIRS to control DLL directories on Windows

[dweindl]

Since Python3.8, external DLL directories need to be added via os.add_dll_directory.

This change provides the AMICI_DLL_DIRS environment variable as an alternative way to specify these directories.

Also, upgrades OpenBLAS to 0.3.19 and runs Windows tests on Python 3.8.

[codecov]

Codecov Report

Merging #1637 (9a13ec7) into develop (c15bf1a) will decrease coverage by 4.73%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1637      +/-   ##
===========================================
- Coverage    78.86%   74.13%   -4.74%     
===========================================
  Files           69       25      -44     
  Lines        10713     3518    -7195     
===========================================
- Hits          8449     2608    -5841     
+ Misses        2264      910    -1354     

Flag	Coverage Δ
cpp	?
petab	66.68% <ø> (ø)
python	?

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Impacted Files	Coverage Δ
python/amici/pandas.py	11.62% <0.00%> (-86.63%)	⬇️
python/amici/testing.py	0.00% <0.00%> (-50.00%)	⬇️
python/amici/import_utils.py	47.32% <0.00%> (-39.70%)	⬇️
python/amici/pysb_import.py	57.03% <0.00%> (-36.83%)	⬇️
python/amici/numpy.py	65.21% <0.00%> (-17.40%)	⬇️
python/amici/__init__.py	76.08% <0.00%> (-16.31%)	⬇️
python/amici/setuptools.py	50.00% <0.00%> (-7.70%)	⬇️
python/amici/parameter_mapping.py	69.56% <0.00%> (-6.09%)	⬇️
python/amici/ode_export.py	88.25% <0.00%> (-5.35%)	⬇️
python/amici/gradient_check.py	81.52% <0.00%> (-4.35%)	⬇️
... and 46 more

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
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