HHH-13876 Delete the immutable SingletonStack implementation as its no longer used

hibernate-core/src/main/java/org/hibernate/internal/util/collections/SingletonStack.java

@@ -1,60 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later
- * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
- */
-package org.hibernate.internal.util.collections;
-
-import java.util.function.Consumer;
-import java.util.function.Function;
-
-/**
- * @author Steve Ebersole
- */
-public class SingletonStack<T> implements Stack<T> {
-	private final T instance;
-
-	public SingletonStack(T instance) {
-		this.instance = instance;
-	}
-
-	@Override
-	public void push(T newCurrent) {
-		throw new UnsupportedOperationException( "Cannot push to a singleton Stack" );
-	}
-
-	@Override
-	public T pop() {
-		throw new UnsupportedOperationException( "Cannot pop from a singleton Stack" );
-	}
-
-	@Override
-	public T getCurrent() {
-		return instance;
-	}
-
-	@Override
-	public int depth() {
-		return 1;
-	}
-
-	@Override
-	public boolean isEmpty() {
-		return false;
-	}
-
-	@Override
-	public void clear() {
-	}
-
-	@Override
-	public void visitCurrentFirst(Consumer<T> action) {
-		action.accept( instance );
-	}
-
-	@Override
-	public <X> X findCurrentFirst(Function<T, X> action) {
-		return action.apply( instance );
-	}
-}