allow scrolling of spell info again

[ThePotatomancer]

Summary

Interface "Fix scrolling spell info in spell casting menu"

Purpose of change

spell info scrolling was broken when the spell menu migrated to uilist.
Before this PR the only way to scroll the spell info of spells with long descriptions (like the first circle spells)
was by focusing and scrolling the spell info window with the mouse (which is not obvious as a possibility at all).

Describe the solution

I extracted the already existing scrolling logic in item menu to our helper class cataimgui, and used it both in item menu
and in the casting menu. It uses the existing previous keybinds for scrolling that were defined but non-functioning.

Describe alternatives you've considered

I tried to figure out how to make the scrollbar visible for spell info, but got stumped and decided it's better to leave it for another PR.

Testing

1. create a world with the magicalysm mod
2. once in game, open the debug menu, the player subsection, and the modify spells section
3. filter for 'first circle' to find one of the mana upgrade ritual spells, and edit to learn it at any level
4. open the spellcasting menu, and have the selection hover over the spell
5. use the default keybinds (< and >) to scroll the spell info to show the spell components

I also tested rebinding the keys in the ? menu, and tested that the item menu scrolling still functions as before.

Additional context