Implementation of checkpoint resume.

[levmckinney]

Implements, checkpoint resume adding two new flags --checkpoint_dir and --checkpoint_freq. To allow for saving the state of the data loaders this PR also switches to using torchdata and DataLoader2.

[codecov[bot]]

Codecov Report

Merging #95 (2adbdce) into main (2050703) will decrease coverage by 0.26%. The diff coverage is 73.01%.

:exclamation: Current head 2adbdce differs from pull request most recent head d8484d3. Consider uploading reports for the commit d8484d3 to get more accurate results

@@            Coverage Diff             @@
##             main      #95      +/-   ##
==========================================
- Coverage   78.78%   78.52%   -0.26%     
==========================================
  Files          32       32              
  Lines        1772     1821      +49     
==========================================
+ Hits         1396     1430      +34     
- Misses        376      391      +15     

Impacted Files	Coverage Δ
tests/scripts/test_integration.py	100.00% <ø> (ø)
tuned_lens/scripts/train_loop.py	70.76% <68.86%> (-1.64%)	:arrow_down:
tuned_lens/scripts/ingredients.py	85.46% <93.33%> (+0.99%)	:arrow_up:
tuned_lens/scripts/eval_loop.py	88.69% <100.00%> (+0.26%)	:arrow_up: