Use explicit conversion from WitnessV0KeyHash -> CKeyID

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

src/script/signingprovider.cpp

@@ -183,7 +183,7 @@ CKeyID GetKeyForDestination(const SigningProvider& store, const CTxDestination&
         return ToKeyID(*id);
     }
     if (auto witness_id = boost::get<WitnessV0KeyHash>(&dest)) {
-        return CKeyID(*witness_id);
+        return ToKeyID(*witness_id);
     }
     if (auto script_hash = boost::get<ScriptHash>(&dest)) {
         CScript script;
@@ -191,7 +191,7 @@ CKeyID GetKeyForDestination(const SigningProvider& store, const CTxDestination&
         CTxDestination inner_dest;
         if (store.GetCScript(script_id, script) && ExtractDestination(script, inner_dest)) {
             if (auto inner_witness_id = boost::get<WitnessV0KeyHash>(&inner_dest)) {
-                return CKeyID(*inner_witness_id);
+                return ToKeyID(*inner_witness_id);
             }
         }
     }

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());

src/script/standard.h

@@ -106,6 +106,7 @@ struct WitnessV0KeyHash : public uint160
     explicit WitnessV0KeyHash(const uint160& hash) : uint160(hash) {}
     explicit WitnessV0KeyHash(const CPubKey& pubkey);
 };
+CKeyID ToKeyID(const WitnessV0KeyHash& key_hash);
 
 //! CTxDestination subtype to encode any future Witness version
 struct WitnessUnknown