Add text comparison metrics to Ben's PR

[ntlind]

Improvements

• Add ROUGE and BLEU metrics to evaluate_text_generation
• Make a few minor suggested changes to the PR
• Change back to python-slim from python-alpine since the latter doesn't seem to work with hugging face's dependencies (e.g., pyarrow). Rationale is listed below. Alternatively, we can try to stick with alpine and try manually installing pyarrow's dependencies.
  • We've repeatedly run into dependency issues with python3.10-alpine; first it was scipy, now it's pyarrow. Switching back means shorter build times and fewer dependency limitations
  • We originally switched to alpine because John said that "ubuntu/debian has historically been pretty bad at patching security issues.". This doesn't seem like an overriding concern, and one that matters less in a future world where we're decoupling from Chariot.
  • python3.10-slim is a "Docker Official" image; it seems secure enough for our use.