Update to 1.20.2 & surface merge strategy

[HydrolienF]

• update to 1.20.2
• add a new marge strategy between relative and absolute. (I had many issue with relative)
• config: add a list of bloc that will be copy from custom world into vanilla world in any condition. (Useful for custom ores generation)
• fix gradle wrapper. close #8
• config: add a list of biome where caves will break the world surface.
• display time stats when server is close
• use bukkit generator to define biome. This allow to remove spigot dependency.