provide exported function for generating MTKParameters from user parameter maps

[isaacsas]

In Catalyst we often found it useful to have functionality to take a parameter map and system defaults (or u0 map and defaults) and return the parameter representation used in solvers via varmap_to_vars. Such functionality doesn't seem to exist anymore with the move to MTKParameters, with one instead needing to build a full ODEProblem (or JumpProblem, etc) and then extract oprob.p. It would be nice to have an exported, user-facing function for building p without needing to go through building a full problem.

[ChrisRackauckas]

@AayushSabharwal how feasible do you think this is?

[AayushSabharwal]

ModelingToolkit.MTKParameters(sys, p, u0). The last argument is optional.

[ChrisRackauckas]

Can we get a docstring and a doc page on it? Make it public API?

[AayushSabharwal]

Sure

[isaacsas]

Awesome, thanks!