Add "dynamic" italian scenario & add new flow cap rate limit

[brynpickering]

Since so much of the underlying data remains the same for a "stationary" vs "dynamic" italian model, it seems to make sense to rely on the same model, just with scenarios to add in additional functionality.

This PR adds in a "dynamic" scenario, which involves setting a maximum rate of capacity expansion for certain technologies. This stops massive jumps in technology capacity between investment steps, although setting the rates to something sensible will require some research.

[brynpickering]

This is a nice idea, but I would rename this to "constrained", not dynamic.

Agreed the naming is murky. I'd argue that the "stationary" model is also "constrained" though. It sets a progressively lower available initial capacity per investment step.

Maybe I expunge the dynamic scenario so that it's just the override for adding a maximum new cap rate that's available. I.e. we don't try to define whether the model is stationary, dynamic, constrained, etc.

[irm-codebase]

That would work. Having the distinction between static and dynamic is still useful when testing EoH, though.

We should ensure that the base case is not dynamic in that sense.