Lists of input parameters in initial conditions

[pipliggins]

Re-implementation of #5191 for clearer implementation history

Allows input parameters used as initial conditions to be included within lists of inputs to the solver by converting model.y0 to model.y0_list, and calculating one initial state per input parameter set.

This rolls back a lot of the changes made by #4981 as the functionality is added to all the solvers; the initial_conditions argument added for IDAKLU has been removed in favour of allowing all inputs to be included within inputs.

Fixes #5154 Fixes #5131