Lower G1 minimum full GC interval

We sometimes see a need to do full GC twice within the current 5s interval.
While we should work to improve our allocation pattern for that, it also
seems too conservative to not allow more full GCs, as long as we also get
some real work done. Hence lowering it to 2s here, which would fix the
current problematic cases.

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

@@ -520,7 +520,7 @@ static OverLimitStrategy createOverLimitStrategy(boolean trackRealMemoryUsage) {
                 createYoungGcCountSupplier(),
                 System::currentTimeMillis,
                 500,
-                5000,
+                2000,
                 lockTimeout,
                 fullGCLockTimeout
             );