Better error message when using local detuning without experimental capabilities enabled

[yitchen-tim]

What did you find confusing? Please describe.
If local detuning is not enabled, the local_detuning_parameters is None, and the discretization is not performed. When running a program with local detuning, one would get error All driving and local detuning time series must cover the same time span. (type=value_error)" because discretization is done in driving but not in local detuning. However, the fundamental reason is that local detuning is not enabled. The current error message is confusing and not actionable.

Describe how documentation can be improved
Inform about the experimental capabilities, rather than only throwing error related discretization at a later stage.