Before this change, the editor completion menu and gutter menus reversed their order so that the initial selection is near the user's focus.  This change instead displays these menus in a consistent top-to-bottom order because the following benefits outweigh that benefit:

* Matches behavior of some other editors (Neovim and VSCode).
* Looks better for lexicographic lists.
* Keeps the meaning of keyboard interaction consistent, if the user is anticipating the order of the menu's contents.

Could consider making this configurable in the future if desired.

Closes #25066.

Release Notes:

- N/A