Split Tower Data Plane from Control Plane

rust-camel separates exchange processing (data plane) from component/endpoint/consumer lifecycle (control plane). The data plane uses Service<Exchange> throughout — every Processor and Producer is a Tower service. The control plane uses its own trait hierarchy (Component, Endpoint, Consumer) with richer lifecycle semantics.

Forcing components into Tower's request/response model would break lifecycle operations (start, stop, suspend, health) that don't map to call(). Keeping Tower strictly for exchange processing makes EIP composition idiomatic while giving the control plane the contracts it actually needs.