Centralize logic around which keybind to display (#25215)

Closes #24931

We've flipped back and forth at least once on whether the last or first
added keybinding should be shown in different contexts (See
[this](https://github.com/zed-industries/zed/issues/23621#issuecomment-2614061385)
as well as #23621 and the subsequent #23660)

This PR attempts to pick a side to stick with so that we are at least
consistent until #23660 is resolved and we have a way to determine which
keybinds to display in a manner that is both consistent and not
confusing

Release Notes:

- N/A