v1.22.6-stratum.1-indev.2

What's Changed

• Feature: give each worldgen thread its own generator instead of ThreadLocal fields
• Feature: StratumWorkerInstances, one copy of a generator per worldgen thread
• Fixed: caveRand and chunkRand are plain fields again, so mods that look them up by name find them
• Fixed: GenBlockLayers seeds its rnd shim at setup, so it survives a mod prefix replacing OnChunkColumnGeneration
• Tweak: GenCaves runs generation on the calling thread's worker
• Fixed: preserve vanilla worldgen contracts for mods
• Fixed: keep vanilla fields, methods, constructors, and handler identities visible
• Feature: use per-thread generator instances on the optimized stock path
• Fixed: restore vanilla topology and serial scheduling when foreign code is detected
• Fixed: serialize mod structure-provider callbacks without disabling the whole stage
• Fixed: initialize compatibility state before mod prefixes can replace generation
• Tweak: retain existing worldgen pooling, parallelism, and generation optimizations

by @trevorftp in #231

Full Changelog: v1.22.6-stratum.1-indev.1...v1.22.6-stratum.1-indev.2