feat: add docs, renaming, small fixes

sbroad-cartridge/src/cartridge/router.rs

sbroad-core/src/core-router.lua

sbroad-core/src/executor/bucket.rs

sbroad-core/src/executor/engine/helpers.rs

sbroad-core/src/executor/engine/helpers/vshard.rs

sbroad-core/src/executor/protocol.rs

sbroad-core/src/executor/result.rs

sbroad-core/src/executor/vtable.rs

sbroad-core/src/ir/api/constant.rs

sbroad-core/src/ir/api/parameter.rs

sbroad-core/src/ir/explain.rs

sbroad-core/src/ir/expression.rs

sbroad-core/src/ir/expression/cast.rs

sbroad-core/src/ir/expression/types.rs

sbroad-core/src/ir/operator.rs

sbroad-core/src/ir/relation.rs

sbroad-core/src/ir/transformation/equality_propagation.rs

sbroad-core/src/ir/transformation/redistribution/groupby.rs

sbroad-picodata/src/runtime/router.rs