* Add DTR entry with number of visible pairs
* Simplify DTR visible pair counter
- Merge the new PairHandlerInvisibleMessage and PairHandlerVisibleDisposedMessage ;
- Leave alone a bunch of messages that were actually unneccessary.
* Match encodings with the rest of the codebase
* Make the DTR entry opt-in and add explanations
* More reliable publishing of PairHandlerVisible/Invisible
* Simplify things for DTR
* Rework async
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