Liquidity baking

Now !2765 (merged).

Context

TZIP draft

Agora comments

Manually testing the MR

Build and run in sandbox. The CPMM and liquidity token contracts are originated during stitching along with a sample FA1.2 contract (in place of tzBTC).

The escape hatch can be invoked through a per_block_votes JSON file (that can be used for changing constants in a future upgrade), e.g. tezos-baker-alpha --votefile "per_block_votes.json" where per_block_votes.json contains {"liquidity_baking_escape_vote": true}.

Unit tests can be run with dune exec src/proto_alpha/lib_protocol/test/main.exe -- test "^liquidity baking$".

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Provide automatic testing (see the testing guide).
• Add item in the Development Version section of CHANGES.md (only for new features and bug fixes).

Reviewers

@galfour @klakplok @ZaynahDargaye @rafoo_ @mbouaziz @tomjack