Function to allow initial condition problem in PETSc to be debugged

[dallan-keylogic]

After once again having to go into PETSc and manually edit the function to return the Pyomo block that it uses for solving the initial condition problem, I think it's time to streamline the process so that people that don't know how to edit core IDAES functions can also debug their initial condition problems.

I know that @Robbybp had a similar request a few months ago. If you have anything in particular you want out of such a helper function, please add it to this issue so that I can keep track of it.

[lbianchi-lbl]

#1443 covers a portion of this PR, but does not implement the refactoring (e.g. introducing a PETSc class) that would be needed (or at least useful) to address this in a more general way.