Add config option allowing map loader to prefer RPG Maker files

[ianling]

Adds a new boolean to the player config: PreferEasyRpgMapFiles (default: true)

This makes the map loader attempt to load EasyRPG map files first, and fall back to RPG Maker map files on errors. Since it defaults to true, this PR retains the existing behavior of the EasyRPG Player, which attempts to load EasyRPG map files first.

I just wanted a way to turn this behavior off in my game, as it creates issues with my VCS setup (essentially, a pre-commit hook that runs lcf2xml on all the files in the project).

QA steps I tried:

• New option set to the default of 1 (true) in config:
  • .emu and .lmu present -> Player loads .emu ✅
  • .emu present, .lmu not present -> Player loads .emu ✅
  • .emu not present, .lmu present -> Player loads .lmu ✅
  • .emu and .lmu not present -> Player crashes with expected error (Error: Loading of Map Map0001.lmu failed. -- notice it loaded the .lmu last) ✅
• New option set to 0 (false) in config:
  • .emu and .lmu present -> Player loads .lmu ✅
  • .emu present, .lmu not present -> Player loads .emu ✅
  • .emu not present, .lmu present -> Player loads .lmu ✅
  • .emu and .lmu not present -> Player crashes with expected error (Error: Loading of Map Map0001.emu failed. -- notice it loaded the .emu last) ✅
• New option missing from config uses default value (1) ✅