Removes jQuery from todos icon related code

What does this MR do?

Rewrites in plain JavaScript the code that triggers an event to update the todos icon badge counter and the listener. Adds a Custom Event polyfill for IE. Fixes some of the changed files to pass our eslint rules.

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

#23022 (moved) #23495 (moved)