* Rework HU_UpdatePatch to HU_UpdateOrBlankPatch with a "required" boolean.
* If desired graphic is not present in resources:
* If required is true, return `missingpat`.
* If false, return NULL as before (font compatibility).
* Add an alias with the previous function signature, so you don't need to add a million `true`s everywhere.
* Remove a ton of irrelevant graphics the game attempts to cache only because of code inherited from vanilla SRB2.
* Remove the unused hudinfo system, also inherited from vanilla SRB2.