Substrait ExecutionPlan Serialization

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
Serialize physical plans, AKA, `ExecutionPlan`s as Substrait plans.

**Describe the solution you'd like**
Expose Substrait consumers and producers for `ExecutionPlan` to allow for encoding to and decoding to / from Substrait.

**Describe alternatives you've considered**
Using LogicalPlans only.