runtime/flow: Remove runtime/flow.
runtime/flow: Remove runtime/flow.

We are no longer relying on this super-interface of Flow to expose
the VC Data Cache.

Change-Id: Icc77ae8042df55b452026161aa9edf91ac14a4a6

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref