Fix sequence size and compute_validation_tests

[isaacmg]

The goal of this PR is to do the following

• Correct a bug where forecast_length was not being passed to `simple_dec
• Fix bugs related to the unscaled_test_loss
• Add unit tests to validate compute_validation logic explicitly.

[codecov]

Codecov Report

Merging #264 (33b6c02) into master (308dc3c) will increase coverage by 0.02%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master     #264      +/-   ##
==========================================
+ Coverage   69.54%   69.57%   +0.02%     
==========================================
  Files          56       56              
  Lines        3526     3536      +10     
==========================================
+ Hits         2452     2460       +8     
- Misses       1074     1076       +2     

Flag	Coverage Δ
python	69.57% <85.71%> (+0.02%)	⬆️

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Impacted Files	Coverage Δ
flood_forecast/basic/linear_regression.py	76.36% <50.00%> (-2.07%)	⬇️
flood_forecast/pytorch_training.py	76.39% <100.00%> (+0.62%)	⬆️

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[isaacmg]

This #265 #253

[isaacmg]

Update there is still an ongoing problem that I can't figure out where in the cases of unscaled_test_loss MSE seems to be double DilateLoss in pretty much every training session. This is try in every logging for some reason. This isn't the case for the scaled_test. At the moment I believe the scaled_test_loss is correct. Additionally when un-scaling the scaled_test_loss it often doesn't equal the scaled_test_loss.