Objectives missing subspace (min time)

[andgoldschmidt]

Describe the bug
Fidelity constraints might be placed in subspaces, and min time needs to allow final_fidelity to be a constraint on the subspace.

Additional context
Ideally, U_goal for problem templates should also be defined in subspaces. This would avoid the need to embed the operator into a zeros space.

That being said, it would be nice to have embed and truncate utilities to automate this process of moving between the subspace and the bigger space, for the standard case of guard levels, if it is needed.

[aarontrowbridge]

I can tackle this if you haven't started on it yet, might be a next week thing though.

[andgoldschmidt]

I just added the min time subspaces into the recent PR allowing optional unitary infidelity Hessians #62

This issue is still open because the U_goal should still be defined in the subspace.

[aarontrowbridge]

this was resolved in v0.2.0