Re-enable all structures in Flat/Superflat worlds for Bedrock 1.26+

Since Bedrock 1.21.80+ and currently in Preview 1.26.13, Flat/Superflat worlds no longer generate key structures like Ancient Cities, Strongholds, Trial Chambers, and Woodland Mansions. This happens even with behavior packs and feature_rules trying to force them. This change breaks creative, technical, and testing gameplay. Many builders, redstoners, and map makers use flat worlds specifically to test and showcase structures without terrain interference. Previous versions (1.21.62 and below) allowed full structure generation in flat worlds using behavior packs. The removal in 1.26.x was not documented in changelogs. Suggestion: 1. Re-enable all structure generation in flat worlds by default, or 2. Add a world creation toggle "Generate All Structures" for Flat worlds, or 3. Add a gamerule: /gamerule generateFlatStructures true This feature is critical for the technical and creative community. Please consider restoring it in 1.26.14+. Versions tested: 1.26.12, 1.26.13 Preview Platform: Minecraft Bedrock Preview Android