feat: use nvim_buf_set_extmark for vim.highlight (#16963)

Closes https://github.com/neovim/neovim/issues/13647

This allows customizing the priority of the highlights.

* Add default priority of 50
* Use priority of 200 for highlight on yank
* use priority of 40 for highlight references (LSP)

runtime/lua/vim/lsp/util.lua

@@ -1550,7 +1550,10 @@ do --[[ References ]]
                       reference_ns,
                       document_highlight_kind[kind],
                       { start_line, start_idx },
-                      { end_line, end_idx })
+                      { end_line, end_idx },
+                      nil,
+                      false,
+                      40)
     end
   end
 end