Have circuit breaker succeed on unknown mem usage

With this commit we implement a workaround for
https://bugs.openjdk.java.net/browse/JDK-8207200 which is a race
condition in the JVM that results in `IllegalArgumentException` to be
thrown in rare cases when we determine memory usage via `MemoryMXBean`.
As we do not want to fail requests in those cases we always return zero
memory usage.

Relates elastic#31767

server/src/main/java/org/elasticsearch/indices/breaker/HierarchyCircuitBreakerService.java

@@ -251,7 +251,15 @@ private ParentMemoryUsage parentUsed(long newBytesReserved) {
 
     //package private to allow overriding it in tests
     long currentMemoryUsage() {
-        return MEMORY_MX_BEAN.getHeapMemoryUsage().getUsed();
+        try {
+            return MEMORY_MX_BEAN.getHeapMemoryUsage().getUsed();
+        } catch (IllegalArgumentException ex) {
+            // This exception can happen (rarely) due to a race condition in the JVM when determining usage of memory pools. We do not want
+            // to fail requests because of this and thus return zero memory usage in this case. While we could also return the most
+            // recently determined memory usage, we would overestimate memory usage immediately after a garbage collection event.
+            logger.info("Cannot determine current memory usage due to JDK-8207200.", ex);
+            return 0;
+        }
     }
 
     /**