Execution Engine Stateright Prototype

[isheff]

Building on the english spec, construct a prototype version of the Execution Engine in the Stateright framework. This may involve some kind of "dummy" Taiga API. Ideally, this would match up with the formal spec.

This will have to match up with the Heterogeneous Paxos Stateright Prototype and the Heterogeneous Narwhal Stateright Prototype to be useful.

Prerequisites

• https://github.com/anoma/specs/issues/123
• Heterogeneous Paxos Stateright Prototype  #45
• Heterogeneous Narwhal Stateright Prototype #44
• Taiga-Typhon Simple Execution Server #56

Sub-Tasks

• Shards
• Executors
• Full-Nodes?
• Garbage collection messages