Allow for reporting delays in line list simulation

[joshwlambert]

Adding reporting delays will allow methods that can account for reporting delays (e.g. {EpiNow2}) to be tested using data simulated with sim_linelist().

[joshwlambert]

This feature should mirror the functionality for reporting delays in {EpiNow2}. In {EpiNow2} there is an adjustment for reporting delays (where all dates are shifted by a reporting delay), and an adjustment for truncation (where the recent cases are underreported as they haven't been put into the line list yet).

Both features should be optional in {simulist}.