Qt::MouseButton supports up to 24 extra buttons Krita currently doesn't recognize. These are found on gaming mice and some tablets will default their device buttons into that range. Its also more convenient to remap a tablet that exposes mousebuttons into ExtraButtons instead of depending on a mapping program to convert mouse buttons into key events (which is a bit lacking in availability on Wayland or in the libinput tablet driver).
This diff fixes two spelling mistakes and introduces some macros to support all the MouseButtons Qt provides (copy pasting ExtraButtonN 21 times would be a bit tedious).
Fixes BUG: 386202
There is at least one outstanding issue to be rectified before this could be merged - this breaks KisStrokeShortcut::priority by having buttonscore take up 24 bits because the buttons are all bitflags. You can't really make it just take buttons by number (1-24) because the code is meant to avoid priority ties by masking the buttons in the shortcut.
That being said, you can already cause a tie by having two shortcuts for the same action with the same buttons and the same number of modifiers. Reading through the revision history this has been revised several times. So maybe avoiding ties isn't that important if we just used the buttons by number or used the count of buttons since it would still take some effort to cause ties.