Move {{pfs_visit}} table updates from {{iic}} to {{gen2}}

There is an instrument-wide pfs_visit table, to which iic appends a row when it consumes a new visit (from the gen2Actor). In normal operations, lower-level actors (sps, fps, agc) get passed that visit as a command argument, and the tables they are responsible for join to the row in pfs_visit

When those lower-level actors get called directly, they are not given a visit argument and request one themselves. There is a common library routine to do this. But it does not update the pfs_visit table.

This ticket is to move the pfs_visit update from iicActor to gen2Actor, so that the table is updated no matter where the request comes from. It could be put into the library code, but I think it would be better to keep the gen2 allocation and the opdb update essentially atomic.