Add interpolations for MIRK methods

[ErikQQY]

Fix #111

This PR adds interpolations for MIRK methods

Tested on example problem from README:

[ChrisRackauckas]

Can you add a convergence with something like a mid time condition in order test the correctness here?

[avik-pal]

This only adds interpolation to the solution object, right? We need the intermediate objects passed to the bc to be interpolation-friendly as well.

[ChrisRackauckas]

Yes, that sol object is what you should just be passing to the bc anyways, just then updating its coefficient vectors as you go along.

[avik-pal]

This would also be a breaking change, right? We can up the SciMLBase compat to 2.0 and do that together with #109 & SciML/SciMLBase.jl#477

[ChrisRackauckas]

Why would this be a breaking change?

[avik-pal]

That changes the input specification to bc. The current specification is a vector of arrays which now changes to a solution similar to shooting.

[ChrisRackauckas]

It was supposed to always be the solution. The solution type acts as a vector of arrays so the actions are the same, just extended though?

[ChrisRackauckas]

this 1 seems odd?