Interop: cleanup derived-from state in interop-deriver (devnet 2)

[protolambda]

The interop-deriver maintains intermediate state, to tell which local-safe L2 block was derived from which L1 block, so it can pass on cross-safe events, for the pre-interop finalizer to work.

Once we implement #11672 we can likely get rid of this intermediate state. Or if we do not, we should at least modify the pruning, to handle reorgs.