[Minor] Migrate src/plugins/lua/neural.lua to lua_shape

[Minor] Migrate src/plugins/lua/neural.lua to lua_shape

Replace tableshape with lua_shape in neural plugin.

Changes:
- ts.shape { ... } → T.table({ ... })
- ts.string, ts.number → T.string(), T.number()
- ts.array_of(x) → T.array(x)
- :is_optional() → :optional()
- Added comprehensive documentation to all fields

Schema: redis_profile_schema for neural network profiles stored in
Redis, including digest, symbols, version, and optional distance.