Add a button to fold/expand all actions in the Input Map

[ArnaudUNC]

For a better overview of all the actions when there are many in a project.

Example: go from this ↓

To this ↓ (and vice versa) with a single button click

[aXu-AP]

This is a good functionality, altough as an alternative it could be triggered by ctrl + open/close one of the items. Similiar shortcut is used at least in Photoshop to open/close all layer groups (altough there it's ctrl+alt+click).

[timothyqiu]

Ctrl+Click sometimes also mean revealing the current branch. So we probably need a switch on Tree.

[Mickeon]

I feel like #4910 would intrinsically solve this without requiring additional buttons/shortcuts.