Fix selected item name not being visible in some menus

[moxian]

Summary

Bugfixes "Fix currently selected item not being visible in some menus"

Purpose of change

Fix this:

Fixes #77368
Fixes #77503

Describe the solution

Cache entries' context less agressively - only when it is first read (i.e. when the menu is being rendered), and not immedaitely on construction (when it is still being prepared).
See

Cataclysm-DDA/src/item_action.cpp

Lines 354 to 355 in cfe9f6c

	kmenu.addentry_desc( num, enabled, bind, ss, desc );
	kmenu.entries[num].ctxt = ss_ctxt;

for an example of breaking code

Describe alternatives you've considered

Use getter/setter for setting .txt / .ctxt which would invalidate the cache at even more appropriate times. But that would mean working with getters/setters...

Testing

Additional context

Originally broken by #76346 . Current PR does not reintroduce the problems #76346 was solving.

Astyle adds an extra indentation level to the whole of struct uilist_entry { now that I've marked the cached fields as private. I don't know if I should let them be public (to negate the diff) or if the indent is fine. Lemme know if i should change this.

[db48x]

This looks great, but you should fix that warning about the duplicate public access specifier (structs are public by default).