Allow Custom Y Limits for Dimensions

Minecraft Bedrock should allow creators to define custom minimum and maximum Y limits for dimensions instead of forcing every custom dimension to use the same vertical range as the Overworld. For example, a dimension could use a range such as Y 0–128 like the Nether, Y -64–192, or another reasonable range chosen by the creator. This could be exposed through the dimension or world-generation configuration with values such as min_y and height. Blocks, terrain generation, structures, spawning, lighting, and the build limit should automatically respect the selected vertical range. The system should also prevent invalid configurations and provide safe limits so creators cannot generate dimensions that would cause instability. Dimension-specific height limits would make custom dimensions much more unique. Creators could build compact underground dimensions, tall sky dimensions, Nether-like worlds, or specialized challenge dimensions without relying on teleportation barriers or artificial borders. This would greatly expand Bedrock add-on world-generation possibilities while using a concept that already exists naturally in Minecraft's dimensions.