Module table improvements 3: offload storage to LMDB

Since the set of modules only grows, it would make sense to move all module data into the LMDB database, instead of the block state. Alternatively, just the module source could be kept in the block state, and the compiled artifact and metadata could be retained in the LMDB database. This would reduce the amount of data that needs to be copied on protocol updates. This is probably more pertinent in the context of a light node, if we continually roll the block state database, as it avoids having to roll the modules as part of that.

The issue names no files, tests, or entry points. Start by locating module storage, block-state handling, and LMDB integration, then clarify whether source stays in block state while compiled artifacts and metadata move to LMDB; done means reducing data copied during protocol updates, especially for light nodes.

Written by the indexing model from the issue text.