the tria_io private subpackage had some unexpected error handling

[dkuegler]

• if IO failed, the functions just returned None instead of raising an exception (which would be best practice) --> changed this to raising IOError exceptions, so proper error handling is possible
• several messages meant for debugging were hard-coded, specifically the local verbose variables, best practice would be to handle this type of logging through the logging module

[codecov]

Codecov Report

Attention: 39 lines in your changes are missing coverage. Please review.

Comparison is base (98b6d7b) 35.01% compared to head (dccd831) 34.92%.
Report is 6 commits behind head on main.

Files	Patch %	Lines
lapy/_tria_io.py	11.36%	39 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #50      +/-   ##
==========================================
- Coverage   35.01%   34.92%   -0.09%     
==========================================
  Files          14       14              
  Lines        2362     2365       +3     
  Branches      301      297       -4     
==========================================
- Hits          827      826       -1     
- Misses       1449     1455       +6     
+ Partials       86       84       -2     

Flag	Coverage Δ
unittests	34.92% <11.36%> (-0.09%)	⬇️

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