Update io.py to change metadata dates into a more readable format

[claaslendt]

Hej everyone,

I am unsure about the current dateformat for the metadata of the GT3X files. It may be more user friendly if the date is formatted into a more readable datetime format instead of .NET ticks.

I changed the _format_time function inside io.py accordingly.

[Trybnetic]

Thanks for pointing that out and I agree that the datetime format here is a better choice. However, I am a bit unsure whether its best to format the np.datetime64 object as str, given that you might want to further use the meta data dict? Also the test_loading_metadata test in tests/test_io.py fails now because of the failed format and needs adjustment.

[claaslendt]

I'd say it's somewhat cleaner this way and potentially more flexible. I have updated the test_io.py to reflect the change.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.02%. Comparing base (79b8384) to head (a59f7bd).
Report is 1 commits behind head on main.

Additional details and impacted files

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  Coverage   72.02%   72.02%           
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  Files           8        8           
  Lines         579      579           
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  Hits          417      417           
  Misses        162      162           

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[Trybnetic]

I played a bit around with it and agree that it is cleaner and for most applications anyway better to have it as a string.

Thanks again for this PR!