Add symbols editor

[Frostbyte0x70]

Adds a new screen that can be used to view and edit the value of data symbols defined in pmdsky-debug. Requires https://github.com/SkyTemple/skytemple-files/pull/505.

The new screen supports editing values as text. Symbols of known enum types use dropdowns or autocomplete textboxes, so the user can check the list of valid values. Boolean values use checkboxes. If the user inputs an invalid or out of range value, an error message is displayed.

Now that this editor exists, I see little purpose for the view located under Patches > Symbols. Maybe we should consider removing / hiding it.

I also think that Lists > Misc. Settings is outdated now, and I wouldn't mind removing it, mainly because:

• All the values listed there can already be edited in this new screen, which isn't much harder to navigate
• The Misc. Settings view contains arbitrary fields
• Any future changes to those symbols in pmdsky-debug will not be reflected on the Misc. Settings view unless manually updated
• The input for belly lost per turn cannot handle negative values, unlike the one in the new symbols view But I don't have a strong opinion on the matter, it's just a suggestion.