Touchups to spellcasting behavior and UI

[chaosvolt]

Summary

SUMMARY: Bugfixes "Spellcasting menu cancels out early if all spells out of energy, don't show max mana unless you actually know a mana-casting spell"

Purpose of change

This fixes two bits of weirdness with spellcasting and associated UI.

Describe the solution

1. In handle_action.cpp, changed cast_spell so that the "check if you're too out of energy to cast any spells" check to properly return out of the function instead of continuing, fixing the issue where it would say "you can't cast any of the spells you know" but still open to a menu of currently-uncastable spells.
2. In panels.cpp, changed spell_panel to check the player's known spells for any mana-casting spells to determine if it returns true. This fixes it so that mana and max mana only shows on your sidebar if one of your spells actually costs mana.

Describe alternatives you've considered

I'm not 100% sure if vector-ifying avatar's known spells and running some for logic on them will have any performance impact over the previous "check a bool on the avatar that will in turn check their known spells" method.

Testing

1. Compiled and load-tested.
2. Started up a world with Magiclysm.
3. Tried to cast with no spells available, same message as usual shows up.
4. Read up a scroll of Megablast, confirmed mana display did not show up since it costs stamina.
5. Rigged my stats and skills so I could actually cast it, confirmed it prevents opening the spell menu after I drain my stamina.
6. Read a scroll of Mana Beam, confirmed that now the mana display pops up.
7. Spammed my way through my mana reserves and depleted stamina again, confirmed that spell menu only cancels early when I don't have the resources for any of my spells.
8. Checked affected files for astyle.

Additional context

[DarianLStephens]

Oh, I'm not sure how I feel about not opening the spell list when none of your spells have the mana needed to cast.
I might still like to look at the list to know how close I am to being able to use something, even if I can't right now, instead of needing to guess or remember the value.
It'd be like hiding all guns in your inventory if you didn't have the ammo for any of them. You could easily forget what you have available, and what you need to use them.

I could be misunderstanding this change, though, and that's not what's actually happening?

[chaosvolt]

Hmm. That's...a good point actually. The problem this fixed was it printing a useless message that doesn't matter until after you've closed the spell menu (by which time you already know you can't cast any of the spells on your menu), but just eliminating the message outright and letting you view your spell menu would work as an alternative solution.