Discard function matches that appear after the current cursor in completions

[thecrypticace]

Look, it's not a fancy shiny new feature without a bug 😅

When we discover function matches via tailwindCSS.classFunctions we were implicitly breaking some assumptions used by the completions code:

• No matches for class attributes or functions that appear after the cursor position are found (we weren't discarding these function matches but we need to)
• The last match is always the one that corresponds to the current cursor position (we collect function matches separately so the order was wrong)

This PR fixes this by doing two things:

• Discarding function matches that appear after the current cursor position
• Sorting the list of attribute and function matches so the last one in the list is always the latest one in the document (up to the cursor)