Replace bootstrap caret with fontawesome caret

What does this MR do?

1. Replaces all occurrences of .caret with fontawesome's caret (fa-caret-down for most cases)
2. Remove .caret from CSS
3. Refactored pipeline graph toggle to display the correct fontawesome caret (Had to change some JavaScript for this)

Are there points in the code the reviewer needs to double check?

• Need to check if I missed any pages 😥 or for any side effects

Why was this MR needed?

Resolves UI inconsistency

Screenshots (if relevant)

Before (1 example out of many):

After:

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #21169 (closed)