Release delegate ref in Releasables#releaseOnce

Like elastic#92452 and elastic#92507 but for `Releasables#releaseOnce`: there's no
need to keep hold of the wrapped releasable after closing it, and in
some cases this might hold on to excessive heap. With this commit we
drop the reference to the delegate when it's complete.

libs/core/src/main/java/org/elasticsearch/core/Releasables.java

@@ -10,7 +10,7 @@
 
 import java.io.IOException;
 import java.io.UncheckedIOException;
-import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
 
 /** Utility methods to work with {@link Releasable}s. */
 public enum Releasables {
@@ -98,13 +98,14 @@ public static Releasable wrap(final Releasable... releasables) {
     }
 
     /**
-     * Wraps a {@link Releasable} such that its {@link Releasable#close()} method can be called multiple times without double releasing.
+     * Wraps a {@link Releasable} such that its {@link Releasable#close()} method can be called multiple times without double-releasing.
      */
     public static Releasable releaseOnce(final Releasable releasable) {
-        final AtomicBoolean released = new AtomicBoolean(false);
+        final var ref = new AtomicReference<>(releasable);
         return () -> {
-            if (released.compareAndSet(false, true)) {
-                releasable.close();
+            final var acquired = ref.getAndSet(null);
+            if (acquired != null) {
+                acquired.close();
             }
         };
     }