Standarize file and function names

[Frostbyte0x70]

Names for files and functions are a mess right now. Some files are named in PascalCase, some in camelCase. Some functions are prefixed by fn_, some are not, some have a name that doesn't match their pmdsky-debug names... All of this should be standarized.

• Use PascalCase for all the .asm files. Check if this change requires changes in SkyTemple's patch definitions.
• Remove the fn_ prefix from all the function labels.
• Check for functions that are already documented in pmdsky-debug and rename them to match the name they have there.