* op-supervisor: Introduce pipeline concept and stage to handle all blocks on head update

* op-supervisor: Simplify to just call a block processor directly

* op-supervisor: Simplify further to remove pipeline entirely and hook up processor

* op-supervisor: Separate out and test the head update callback.

* op-supervisor: Fetch receipts for each block

* op-supervisor: Create clients and monitor chain heads for each L2 chain

* op-supervisor: Remove rpc url from log message

* op-supervisor: Update tickets in TODOs