Fixed Sync/Timestamp + Packets-->Segments Backtracking

[seg188]

• Fixed issuing of timestamp packets (more closely matches real data with {almost} 1:1 matching data:timestamp)
• Fixed issuing of sync packets (incorrect packet ordering and issue frequency) + rollover for sync packet timestamp
• Fixed backtracking for packets-->Segments

[krwood]

Looks great! Thanks for catching these subtle bugs Stephen! Would be great to post some of the validation plots here for the record, but this is good to go.

[seg188]

Before the changes in this PR, we saw that the validation code was reporting that reconstructed charge events were not ~1:1 with true events:

This issue was two fold. Firstly, due to a bug in the packet-->segment backtracking where the index of the segments was stored instead of the segment_id from edep-sim, the actual backtracking was giving the wrong event IDs. The second issue was with the sync packet logic--the packets were issue every 1e8 instead of 1e7 due to a mis-conversion of clock ticks to microseconds. The effect of this is most obvious when trying to use the sync to reconstruct the global timestamp (packet timestamp + rollover). The previous behavior is here (note duration is shorted than expected 231 seconds, and timestamps are not monotonically increasing):

Corrected behavior is here:

Finally, the corrected behavior associating events: