["model"] Check impact of latent period delay from infectious to hospitalized on model dynamics and forecasts

### Summary

There's no a priori reason to assume that transition of a person from the Susceptible to Infectious states corresponds with immediate development of symptoms requiring hospitalization. If there's a separation in time, then the model may be mis-predicting spread in the region by initializing `I` based on present-day hospitalizations.

We need to check whether accounting for this affects relevant forecast outputs.

### Additional details

### Suggested fix

Shift the initialization from current hospitalizations to community infection rate back in time by a configurable `latent_period`, and then shift forecast admissions of newly-infected individuals forward in time by that same `latent_period`