Resolve "Integrate rb-ipynbdiff into Gitlab"

Why

Code reviewing Jupyter Notebooks is currently not possible, and a pain point for our users.

Epic: &6589 (closed)

What

• Adds a dependency to rb-ipynbdiff (https://gitlab.com/gitlab-org/incubation-engineering/mlops/rb-ipynbdiff)
• When displaying diffs, detects a ipynb file and converts the blobs to a markdown version
• When displaying diffs, creates a new diff based on the markdown version

Screenshots

	Before	After
Diff
MR

Testing

• Clone https://gitlab.com/gitlab-org/incubation-engineering/mlops/ipynb-test-projects/diff-sample
• Navigate to the first commit diff
• The diff should be displayed as the before screenshot above, since the feature flag is disabled
• Enable the feature flag:
  • Open the rails consoles (rails c)
  • Feature.enable(:jupyter_clean_diffs)
• For MR, create a merge request from branch adding_new_file into main
  • Make sure the feature is enabled

Concerns

• We understand this is a heavy operation to be added at request time. We are currently exploring alternatives on how to enable special diff rendering for varied file types on this issue: #342143 (closed)
• At the moment we generate the diff, we have already fetched the info from gitaly, so the limits of file size area already applied at this point