Rework states, fixed children, and storage logic [stage]

core/src/main/java/io/xpipe/core/store/FixedChildStore.java

@@ -0,0 +1,6 @@
+package io.xpipe.core.store;
+
+public interface FixedChildStore extends DataStore {
+
+    int getFixedId();
+}

core/src/main/java/io/xpipe/core/store/FixedHierarchyStore.java

@@ -4,5 +4,5 @@ import java.util.Map;
 
 public interface FixedHierarchyStore extends DataStore {
 
-    Map<String, DataStore> listChildren() throws Exception;
+    Map<String, FixedChildStore> listChildren() throws Exception;
 }

core/src/main/java/io/xpipe/core/util/FailableBiConsumer.java

@@ -0,0 +1,7 @@
+package io.xpipe.core.util;
+
+@FunctionalInterface
+public interface FailableBiConsumer<T, U, E extends Throwable> {
+
+    void accept(T var1, U var2) throws E;
+}

core/src/main/java/io/xpipe/core/util/FailableConsumer.java

@@ -0,0 +1,7 @@
+package io.xpipe.core.util;
+
+@FunctionalInterface
+public interface FailableConsumer<T, E extends Throwable> {
+
+    void accept(T var1) throws E;
+}

core/src/main/java/io/xpipe/core/util/FailableRunnable.java

@@ -0,0 +1,7 @@
+package io.xpipe.core.util;
+
+@FunctionalInterface
+public interface FailableRunnable<E extends Throwable> {
+
+    void run() throws E;
+}