feat: Add utility class migration script

This adds a migration script for legacy utilities to tailwind utilities.

This was extracted from:
gitlab!154442



The idea is simple:
1. We give a list of files via stdin or iterate over all source files in
   the current directory or in a given list of directories.
2. We replace legacy utility class names with their tailwind equivalents
   (list maintained `bin/lib/tailwind_equivalents.js`). Note, not all
   legacy utils are mapped, but just the ones currently in use in the
   GitLab project and other important projects.
3. You test that the changes have the expected results. Migration
   strategy for larger projects might be folder by folder or route by
   route.

Co-authored-by: Mark Florian <mflorian@gitlab.com>
Co-authored-by: Paul GV <pgascouvaillancourt@gitlab.com>