cleanup and combine single parent priority allocation

src/main/java/tenor/ISingleParentPriorityAllocator.java

@@ -0,0 +1,28 @@
+/*
+ * This file is part of Baritone.
+ *
+ * Baritone is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Baritone is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Baritone.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package tenor;
+
+public interface ISingleParentPriorityAllocator extends IQuantizedTask {
+    @Override
+    default IQuantityRelationship priority() {
+        if (parentTasks().size() != 1) {
+            throw new IllegalStateException();
+        }
+        return parentTasks().get(0)::allocatedPriority;
+    }
+}