Export text utils as ES6 modules

What does this MR do?

• Export text utils as ES6 modules
• Breaks utils and markdown functions into 2 files
• Removes latinise: https://gitlab.com/gitlab-org/gitlab-ce/issues/40018
• Adds unit tests for the utils functions
• Documents test utils functions
• Removes non used utils functions
• Enables some eslint rules

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/40018

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/37851

https://gitlab.com/gitlab-org/gitlab-ce/issues/38869