Load LST into VisitInfo tickets/DM-8052

[parejkoj]

Adding LST into VisitInfo, by way of a "fake" ERA.

[r-owen]

Using a named tuple is an improvement. I am not convinced using explicit data1/data2 instead of a list of data is an improvement, but it will be easy to revert if we ever decide we want additional data.

[parejkoj]

I agree that the *1/*2 split wasn't necessarily an improvement, but I wasn't sure how best to handle the non-visitInfo data (HA/LST) that we're also checking. As you say, it's easy enough to bundle all the data values into a tuple if we want.