feat(#1798) Performance fix for topic send

[jeanouii]

To be discussed

[cshannon]

@jeanouii - This is an interesting find, I didn't even notice that synchronized keyword on that method. Most of the synchronization happens internally on the various collections etc. and I looked and I didn't see synchronized use anywhere else on the topic object itself internally.

Did you look around the broker to see if anything happens to synchronize the topic externally? The destinations often get referred to more generic as RegionDestination plus there's various wrappers so saerching might be tricky. I will search too, I just am curious if anything else is synchronizing on the Topic's intrinsic lock that would now break if we switch the lock.

I guess there's always the risk of breaking existing plugins (if they were synchronizing for some reason on the topic) but we can't control any custom code so not much we could do in that scenario.