Update timestamp from epics inside while(acquire) loop

[jsouter]

Previously noticed that all frames have identical timestamps, the startTime timestamp only gets updated in the first while loop, so within while (acquire) block timestamps are currently the same if collecting more than a single frame.

e: after discussing with @coretl I will push again to this so that the timestamp uses EpicsTS, as the two timestamps are currently separated by some lines of code.

[MarkRivers]

@jsouter I commented on one of your PRs this morning, saying that I created a new asynNDArrayDriver::updateTimeStamps() method. I can’t remember which repository I did that in.

For drivers that update NDArray.timeStamp from the camera info you will need to call the new method first, and then update with the camera timestamp.

[jsouter]

Thanks Mark, I think most of the PRs I've sent so far have just been for the detectors that don't use a hardware time stamp, but I've made note of which other detectors will need changing too. I will update these PRs to use the new updateTimeStamps() method soon.