Add load function to train_util to resume training

[ssenan]

• Resolves Add load function to main train class #151
• Adds a function called load within train_util class that allows checkpoints to be used to resume training
• Small changes to pytorch dataloader params that make training faster

[codecov]

Codecov Report

Merging #152 (f32d438) into main (8776054) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@           Coverage Diff            @@
##            main    #152      +/-   ##
========================================
- Coverage   2.76%   2.73%   -0.04%     
========================================
  Files         12      12              
  Lines        795     804       +9     
  Branches      88      89       +1     
========================================
  Hits          22      22              
- Misses       773     782       +9     

Impacted Files	Coverage Δ
src/dnadiffusion/data/dataloader.py	0.00% <0.00%> (ø)
src/dnadiffusion/utils/train_util.py	0.00% <0.00%> (ø)