notebooks: add compute block scaffolding

Created by: rvantonder

Adds scaffolding to prepare for compute block. Just want to get the types added and boiler for the block. It's not possible to exercise this code yet (no way to add a compute block). Excludes actual functionality, deserialization for GQL/GQL types, and feature flag for compute block. These will come in follow up PRs.

Test plan

Code is not exercisable, no tests yet.