Add bootstrap tailwind equivalents file

What does this MR do?

Adds a bootstrap_tailwind_equivalents.json file that can be used with the migration script to migrate Bootstrap CSS utility classes to Tailwind CSS. It also makes a few minor modifications to the migration script to work with Bootstrap.

I used gitlab!155157 (closed) to verify that all the equivalents are correct. This is the same script I used for the GitLab UI legacy utils and it worked well.

Screenshots or screen recordings

How to test

In GitLab UI

• Build the migration script

yarn build-migration-script

In GitLab directory

• Run the following (update paths to your machine)

/Users/peterhegman/Work/gitlab-ui/bin/migrate_custom_utils_to_tw.bundled.mjs \
  --directories app/assets/javascripts/groups/components \
  --migrations /Users/peterhegman/Work/gitlab-ui/bin/lib/bootstrap_tailwind_equivalents.json