feat: `RateSystem` improvements

[reykboerner]

Following from PR #117, we have the following TODO's to make RateSystem work more generally:

• multi-parameter ramping
• IIP compatibility
• CoupledSDEs compatibility (see RateSystem for CoupledSDEs #205)
• decide how current_parameters should behave

[Datseris]

also reversed forcing via boolean argument

[Datseris]

also re-measure performance difference from hardcoded. It is literally impossible for the hard coded version to be slower. literally.