Rework and simplify module structure

[florentc]

This pull request refactors the module structure in order to get rid of some meta-named modules (Types, Optics, Monad), anti patterns that lead to crowded modules (Misc, Types), legacy unused code (e.g. Balance) or terminology (e.g. Constraints).

The following changes are introduced:

• No more Tx and Constraints parent modules
• Tx.Constraints.Types is split into Output (classes and instances describing transaction outputs) and Skeleton (transaction skeletons)
• Tx.Constraints.Optics was short and dealt with skeletons so its content is now in Skeleton
• Only a few functions from Misc were used by Wallet. They have been moved to that module and Misc has been removed.
• Balance has been removed
• Wallet and RawUPLC are now at the top level: they were not closely linked to the concept of MockChain
• The export modules have been updated accordingly: import Cooked brings everything to scope. The tests use that.
• Tweak module directory is now at the top level, outside of Attack
• The MockChain module is now flat and the Monad module called BlockChain

├── Cooked
│   ├── Attack
│   │   ├── AddToken.hs
│   │   ├── DatumHijacking.hs
│   │   ├── DoubleSat.hs
│   │   └── DupToken.hs
│   ├── Attack.hs
│   ├── Currencies.hs
│   ├── Ltl.hs
│   ├── MockChain
│   │   ├── BlockChain.hs
│   │   ├── Direct.hs
│   │   ├── GenerateTx.hs
│   │   ├── Staged.hs
│   │   ├── Testing.hs
│   │   └── UtxoState.hs
│   ├── MockChain.hs
│   ├── Output.hs
│   ├── Pretty.hs
│   ├── RawUPLC.hs
│   ├── Skeleton.hs
│   ├── Tweak
│   │   ├── AddInputsAndOutputs.hs
│   │   ├── Common.hs
│   │   ├── OutPermutations.hs
│   │   └── TamperDatum.hs
│   ├── Tweak.hs
│   └── Wallet.hs
└── Cooked.hs