Adds the "allowEndOfTransaction" boolean flag to the applyOps oplog entry. The field is optional and not set by default. Currently no code sets this flag. It will later be set conditionally on the final applyOps entry of replica set and single-shard transactions if the allowEndOfTransaction parameter is set at the time of the transaction commit. An equivalent will be added to the oplog entry of sharded transactions.
Change streams can then use this to unambiguously determine the final event in any transaction and also determine if the allowEndOfTransaction parameter was set at commit time.

This is part of SPM-4826.