Problem: Currently vim.hl.range only allows one timed highlight.
Creating another one, removes the old one.
Solution: vim.hl.range now returns a timer and a function. The timer
keeps track of how much time is left in the highlight and the function
allows you to clear it, letting the user decide what to do with old
highlights.
(cherry picked from commit eae2d3b145)
5829b5de0a