Contract Code Freeze ❄️

Major changes

• #337 Add Burn Auction. Thank you, Hermez!
• #336 #343 Immutable Parameters. We assume they will never change once the contracts are deployed.
• #339 Revamp Rollback and properly test it.
• #345 Removed Logger. Logs now emitted from multiple contracts instead of from a monolithic logger contract.
• #346 Make batches a mapping.

Minor changes

• #356 Add deposit helper
• #355 Reduce batch account registration size from 1024 to 16, because waiting for 1024 registrations is too long.
• #349 Add encoders and decoders for creat2transfer with public keys
• #347 Add missing dispute creat2transfer to rollup contract.