Make EventData building based on IEvent synchronization independent from factory instance

Using factory instance for blocking is prone to sync issues. We don't document
possibility to block on IEventDataFactory instance anyway.

DEVSIX-5515

Autoported commit.
Original commit hash: [82e91cf69]

Author: yulian-gaponenko

itext/itext.kernel/itext/kernel/counter/data/EventDataHandler.cs

@@ -81,6 +81,8 @@ namespace iText.Kernel.Counter.Data {
     /// <typeparam name="V">data type</typeparam>
     public abstract class EventDataHandler<T, V>
         where V : EventData<T> {
+        private readonly Object createLock = new Object();
+
         private readonly Object processLock = new Object();
 
         private readonly IEventDataCache<T, V> cache;
@@ -110,8 +112,7 @@ public virtual IList<V> Clear() {
 
         public virtual void Register(IEvent @event, IMetaInfo metaInfo) {
             V data;
-            //Synchronization is left here mostly in consistency with cache and process, but factories are usually not thread safe anyway.
-            lock (factory) {
+            lock (createLock) {
                 data = factory.Create(@event, metaInfo);
             }
             if (data != null) {

port-hash

@@ -1 +1 @@
-427b4ef12f5518f96006747f22ada788b9eb21a7
+82e91cf69ce5955d6e1f9360a4e5b0fecb16151b