Core/Skills: Check if a skill can be unlearned with SkillRaceClassInfo.dbc data and use max skill level from SkillTiers.dbc
Tools/MMapsGenerator: Improve mmaps generation time on multi-core CPUs

Queue biggest maps first for mmaps generation to avoid waiting for last map, usually map id 571.
Fix wrong maps count being printed on startup.
Core/MMAPs: Update recast

Update recast to https://github.com/memononen/recastnavigation/commit/42b96b7306d39bb7680ddb0f89d480a8296c83ff
Previous MMAPs might still work but it's recommended to re-extract them.