* [web] add frontend tests for sharejs transform
* [web] extend tests for sharejs transform to flush eventually
* [web] full coverage for sharejs transform
* [web] add tests for sharejs events
* [web] add tests for sharejs callbacks
* [web] avoid sending empty sharejs op
* [web] add tests for resending after reconnecting
* [web] avoid resending of empty sharejs op after reconnecting
GitOrigin-RevId: 226fe47a7069cb877fd5a60454f86cc5855d9a0e