Adding Ipopt callbacks to DTO (previously implemented in QC)

[gennadiryan]

Fixes harmoniqs/QuantumCollocation.jl#157 (broken following deprecation of QuantumCollocationCore); other PR will build on this to serialize optimizer state as well.

[andgoldschmidt]

@BBhattacharyya1729 does this capture the full spirit of your local callbacks reimplementation?

[gennadiryan]

@jack-champagne Let me know if you like the "take 2" factory pattern better (I included usage examples below; waiting to add my tests once we decide which way to go with this); it seems a bit more flexible wrt writing new callbacks/composing existing callbacks. I had initially written the individual callbacks (_callback_update_trajectory, _callback_rollout_fidelity, etc.) as bare functions which would take their parameters as kwargs (e.g. you pass the problem, system, fidelity threshold, other parameters the callback depends on etc. as kwargs to callback_factory), but that seemed a bit messy because of (a) risk of name collision and more importantly (b) kwargs are not typed in Julia (behind the scenes, type signatures on kwargs are ignored; they're just treated as annotations by the compiler). As a result I reverted to using a factory pattern for everything; imo it's a lot cleaner now, but curious about your thoughts on this.

[jack-champagne]

minor changes! looking good to me

[jack-champagne]

fantastic! let's get this merged. @gennadiryan bump the project toml version number first before you merge.