Re-add kona registry depset test for interop-staging networks

## Context

PR #21679 disabled the kona registry-derived interop depset assertion because the current superchain-registry snapshot does not yet contain a durable interop-staging network to pin against. The previous assertion was tied to transient/devnet registry contents and became unstable when those entries changed upstream.

## Work

When interop-staging networks are present in the superchain registry, add the registry-derived interop cluster test back in `rust/kona/crates/protocol/registry/src/lib.rs`. The test should pin the committed `etc/depsets.json` snapshot against the expected interop-staging cluster membership and keep checking that registry-derived dependency sets use the default message expiry window.

## Acceptance criteria

- `kona-registry` has an active test covering registry-derived interop-staging depsets.
- The test is based on stable interop-staging networks in `superchain-registry`, not temporary devnet entries.
- `cargo test -p kona-registry --lib` passes.