This updates `fmt` to the latest version and moves to just being a copy
of their repo to make updating easier (no editing their cmake / figuring
out which files to minimally include).
The motivation for this is now that we switched to C++ 20, there were a
ton of deprecated function usages that is going away in future compiler
versions. This gets rid of all those warnings.
- decompile `neon-baron-part`, which also has the hideout door for some
reason
- improve a few error messages in static data decompilation
- fix bug with disabling fog in merc
