Updates the `adjusts_mac_shortcuts` function to render shortcuts
with the `Fn` key as a separate html element (e.g. `Fn` + `arrow`)
instead of rendering the shortcut as one block (e.g. `Fn + arrow`).
Also, because keyboard shortcuts should be rendered with each key
as a separate html element, updates `adjusts_mac_shortcuts` to
only change html elements that are an exact match to a keyboard
key. Html elements with whitespace will be ignored (e.g. `Enter`
becomes `Return`, but `Enter or Backspace` is not changed though
it previously would have been changed to `Return or Delete`).
Fixes#22112 (in combination with #22273).
We also update the tippy.js mock in tests to expect a element
(zjquery FakeElement function) instead of zjquery instance, and get
rid of setting _tippy property itself to a noop function.
