lsp: Fix text edits with the same start position (#12434)

According to the LSP spec[1], multiple edits can have the same starting
position, and if that is the case, they should be applied in the order
as they come in the array.

The implementation uses a reverse sort to not interfere with non applied
edits, but failed to take into account the spec.

[1] https://microsoft.github.io/language-server-protocol/specifications/specification-3-14/#textedit

runtime/lua/vim/lsp/util.lua

@@ -92,7 +92,7 @@ local function sort_by_key(fn)
   end
 end
 local edit_sort_key = sort_by_key(function(e)
-  return {e.A[1], e.A[2], e.i}
+  return {e.A[1], e.A[2], -e.i}
 end)
 
 --- Position is a https://microsoft.github.io/language-server-protocol/specifications/specification-current/#position