Properly remove security index recovered state consumer (elastic#112927)

One of the security index state change listeners attempts to remove
itself once it has received the expected event.

However, since the consumer is a lambda, `this` in
`stateChangeListeners.remove(this);` actually refers to the enclosing
class instance (`SecurityIndexManager.this`) which results in a noop and
not an actual removal of the relevant consumer. 

This PR fixes this by converting the lambda to an anonymous class.  

It's technically a bug, but so minor that it doesn't warrant a bug
changelog IMO; so I'm labelling it a non-issue instead.

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/support/SecurityIndexManager.java

@@ -344,13 +344,16 @@ public static int getMigrationVersionFromIndexMetadata(IndexMetadata indexMetada
     }
 
     public void onStateRecovered(Consumer<State> recoveredStateConsumer) {
-        BiConsumer<State, State> stateChangeListener = (previousState, nextState) -> {
-            boolean stateJustRecovered = previousState == UNRECOVERED_STATE && nextState != UNRECOVERED_STATE;
-            boolean stateAlreadyRecovered = previousState != UNRECOVERED_STATE;
-            if (stateJustRecovered) {
-                recoveredStateConsumer.accept(nextState);
-            } else if (stateAlreadyRecovered) {
-                stateChangeListeners.remove(this);
+        BiConsumer<State, State> stateChangeListener = new BiConsumer<>() {
+            @Override
+            public void accept(State previousState, State nextState) {
+                boolean stateJustRecovered = previousState == UNRECOVERED_STATE && nextState != UNRECOVERED_STATE;
+                boolean stateAlreadyRecovered = previousState != UNRECOVERED_STATE;
+                if (stateJustRecovered) {
+                    recoveredStateConsumer.accept(nextState);
+                } else if (stateAlreadyRecovered) {
+                    stateChangeListeners.remove(this);
+                }
             }
         };
         stateChangeListeners.add(stateChangeListener);