Issue #5246 - add Inflater/Deflater pools to server dump

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-util/src/main/java/org/eclipse/jetty/util/compression/CompressionPool.java

@@ -134,4 +134,15 @@ public abstract class CompressionPool<T> extends AbstractLifeCycle
         }
         _numObjects.set(0);
     }
+
+    @Override
+    public String toString()
+    {
+        return String.format("%s@%x{%s,size=%d,capacity=%s}",
+            getClass().getSimpleName(),
+            hashCode(),
+            getState(),
+            _pool.size(),
+            _capacity < 0 ? "UNLIMITED" : _capacity);
+    }
 }