Memory leak fix in ConnectorTracker (#10743)

When finished with upload, streamVariable should be disposed.
Now StreamVariable is removed also from streamVariableToSeckey.
https://github.com/vaadin/framework/issues/10695 #10695

server/src/main/java/com/vaadin/ui/ConnectorTracker.java

@@ -846,7 +846,8 @@ public class ConnectorTracker implements Serializable {
         }
         Map<String, StreamVariable> nameToStreamVar = pidToNameToStreamVariable
                 .get(connectorId);
-        nameToStreamVar.remove(variableName);
+        StreamVariable streamVar = nameToStreamVar.remove(variableName);
+        streamVariableToSeckey.remove(streamVar);
         if (nameToStreamVar.isEmpty()) {
             pidToNameToStreamVariable.remove(connectorId);
         }

server/src/main/java/com/vaadin/ui/Upload.java

@@ -1155,6 +1155,8 @@ public class Upload extends AbstractComponent
                     fireUploadSuccess(event.getFileName(), event.getMimeType(),
                             event.getContentLength());
                     endUpload();
+                    if(lastStartedEvent != null)
+                        lastStartedEvent.disposeStreamVariable();
                 }
 
                 @Override
@@ -1173,6 +1175,8 @@ public class Upload extends AbstractComponent
                         }
                     } finally {
                         endUpload();
+                        if(lastStartedEvent != null)
+                            lastStartedEvent.disposeStreamVariable();
                     }
                 }
             };