Use explicit conversion from WitnessV0KeyHash -> CKeyID

These types are equivalent, in data etc, so they need only their
data cast across.

src/script/standard.cpp

@@ -28,6 +28,11 @@ CKeyID ToKeyID(const PKHash& key_hash)
     return CKeyID{static_cast<uint160>(key_hash)};
 }
 
+CKeyID ToKeyID(const WitnessV0KeyHash& key_hash)
+{
+    return CKeyID{static_cast<uint160>(key_hash)};
+}
+
 WitnessV0ScriptHash::WitnessV0ScriptHash(const CScript& in)
 {
     CSHA256().Write(in.data(), in.size()).Finalize(begin());