Move non-consensus data types to stdlib; better separate commitments and logic validation

[dr-orlovsky]

This is a prerequisite for solving witness transaction blockchain re-org and lightning channel constructions issues. It also unlocks a way for adding contract state introspection and cross-contract interaction.

The PR contains no changes for the logic and validation; it has just module re-arrangements and movement of non-consensus types to stdlib. It also introduces a new trait type for ContractState which fixes the way the standard library must account for the contract state to enforce consensus rules in the standard library - and in the future to use inside AluVM.

This PR is followed by RGB standard library, interfaces, schemata and cli PRs:

• Witness filtering with refactored state management workflow rgb-std#241
• Support new witness filtering rgb#227
• Update to use new stdlib APIs with witness filtering rgb-interfaces#10
• Update to use new stdlib APIs with witness filtering rgb-schemata#45