contractcourt: store new taproot resolution info in new key

We pull the information from the sign descriptors and store them in the
resolutions. However, the resolvers created end up duplicating the
resolution data, so we update the sign descs as needed during start up.

contractcourt/briefcase_test.go

@@ -625,10 +625,7 @@ func TestContractResolutionsStorage(t *testing.T) {
 	diskRes, err := testLog.FetchContractResolutions()
 	require.NoError(t, err, "unable to read resolution from db")
 
-	if !reflect.DeepEqual(&res, diskRes) {
-		t.Fatalf("resolution mismatch: expected %v\n, got %v",
-			spew.Sdump(&res), spew.Sdump(diskRes))
-	}
+	require.Equal(t, res, *diskRes)
 
 	// We'll now delete the state, then attempt to retrieve the set of
 	// resolvers, no resolutions should be found.