Fix handling delayed targets

[michael-nml]

Various fixes for handling data where targets are missing.

The fixes are similar to code referred to in #279 as problematic, so this may introduce issues for specific datasets.

[codecov]

Codecov Report

Patch coverage: 68.47% and project coverage change: -0.05 ⚠️

Comparison is base (842ef57) 83.17% compared to head (6282c99) 83.12%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #306      +/-   ##
==========================================
- Coverage   83.17%   83.12%   -0.05%     
==========================================
  Files          82       82              
  Lines        6431     6489      +58     
  Branches      974      992      +18     
==========================================
+ Hits         5349     5394      +45     
- Misses        819      825       +6     
- Partials      263      270       +7     

Impacted Files	Coverage Δ
...nyml/performance_calculation/metrics/regression.py	90.97% <7.69%> (-9.03%)	⬇️
nannyml/drift/univariate/methods.py	87.81% <14.28%> (-3.40%)	⬇️
nannyml/plots/components/step_plot.py	63.63% <16.66%> (-3.97%)	⬇️
nannyml/drift/ranker.py	91.58% <100.00%> (+0.24%)	⬆️
nannyml/performance_calculation/metrics/base.py	93.93% <100.00%> (+0.12%)	⬆️
...mance_calculation/metrics/binary_classification.py	84.98% <100.00%> (+4.40%)	⬆️
...e_calculation/metrics/multiclass_classification.py	81.62% <100.00%> (+0.61%)	⬆️
...performance_estimation/confidence_based/metrics.py	95.81% <100.00%> (+0.04%)	⬆️

... and 3 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.