feat: include action current keybinding as part of its tooltip

[dalthviz]

Description

When an action has a keybinding set it could be nice to be able to see it as part of the action's tooltip. So, for example, over napari,you can see tooltips formated in the following way:

This is part of the elements that started to be discussed over an exploration to use QModelToolBars for buttons over napari. For more details on that you can see https://github.com/napari/napari/pull/7133

[tlambert03]

find by me 👍