Various changes to precompleted dungeons

[fenhl]

• Fixes a bug reported today on Discord where precompleted dungeon rewards did not account for boss ER
• Makes precompleted dungeon rewards compatible with reward shuffle (rewards in side dungeons or the overworld will have no effect)
• Changes internal terminology from empty to precompleted to avoid potential confusion, as previously discussed at https://github.com/OoTRandomizer/OoT-Randomizer/pull/2244#discussion_r1633280520
• Removes the EmptyDungeons and EmptyDungeonInfo classes in favor of making World.precompleted_dungeons a simple dict[str, bool] like World.dungeon_mq
  • The existence of the EmptyDungeonInfo.boss_name attribute contributed to the aforementioned boss ER bug, it is replaced with calculating the hint area when needed
• Minor drive-by code style fixes