storage: improve controller/cluster protocol

[dseisun-materialize]

This is the epic that captures the work described in the doc here.

• [x] https://github.com/MaterializeInc/materialize/issues/18795
• [ ] https://github.com/MaterializeInc/materialize/issues/23508
• [ ] https://github.com/MaterializeInc/materialize/issues/23510
• [ ] https://github.com/MaterializeInc/materialize/issues/23511
• [ ] https://github.com/MaterializeInc/materialize/issues/23512

Bugs we hope would be fixed:

• [ ] https://github.com/MaterializeInc/materialize/issues/24801

Action log

• 21 February 2024. Slip the release date for this work to May 1, to avoid conflicting with Aljoscha's controller refactoring (https://github.com/MaterializeInc/materialize/pull/24816).