op-supervisor: add StaticConfigDependencySet.Dependencies() getter (ethereum-optimism#15951)

* op-supervisor: add StaticConfigDependencySet.Dependencies() getter

* return copy of ds.dependencies for safety

* more detailed comment

Author: bitwiseguy

op-supervisor/supervisor/backend/depset/static.go

@@ -221,3 +221,16 @@ func (ds *StaticConfigDependencySet) MessageExpiryWindow() uint64 {
 	}
 	return ds.overrideMessageExpiryWindow
 }
+
+// Dependencies returns a deep copy of the dependencies map
+func (ds *StaticConfigDependencySet) Dependencies() map[eth.ChainID]*StaticConfigDependency {
+	copied := make(map[eth.ChainID]*StaticConfigDependency, len(ds.dependencies))
+	for chainId, dep := range ds.dependencies {
+		copied[chainId] = &StaticConfigDependency{
+			ChainIndex:     dep.ChainIndex,
+			ActivationTime: dep.ActivationTime,
+			HistoryMinTime: dep.HistoryMinTime,
+		}
+	}
+	return copied
+}