TAPI Streaming start from latest

[nigel-r-davis]

TR-548 documents the option to start the stream from latest (as opposed to earliest at offset 0), however, there is not a use case explaining this usage. This use case should be added in TAPI 2.7 and should be considered for back propagation to earlier releases.

This approach to stream usage allows the stream to be combined with RESTCONF GET based alignment. It is also useful in some resilience scenarios.