Plan to make Blueprint ergonomic code-wise in the Viewer

[emilk]

Starting in #2010 we will load the blueprint store from the data store each frame, then write it back. This has many sharp edges:

• Things that are #[serde(skip)] will be forgotten between frames
• We need to special-implement PartialEq for some thing due to #[serde(skip)]
• For each new element in the blueprint we need to write code to:
  • Create a new component for it OR add it to an existing struct and change its arrow type in the "mandatory" doc-test
  • Load it from the store
  • Diff it
  • Write it to the store
  • Write a Python interface for it

This will very quickly collapse under its own weight unless we come up with a better plan

Related:

• Tracking Issue: Store Façade #2019

[emilk]

We have a plan: code-gen from Flatbuffers IDL. Generate Python and Rust SDKs including the arrow conversions.

We also have #2188

[jleibs]

Re-opening this until we have line-of-sight on the code-gen flatbuffers IDL actually solving the described painpoints.