Streamline template metaprogramming with libraries

[beojan]

We have a lot of template metaprogramming in Phlex which we could streamline by using Boost CallableTraits and MP11 (or Hana).

This could be done all at once, or we could just work on what's in the metaprogramming directory then improve the rest organically as we change those files elsewhere.

[beojan]

Looked at this, and I can eliminate everything in metaprogramming/detail except ctor_reflect_types.hpp with CallableTraits doing most of the heavy lifting and MP11 filling in the gaps.

[knoepfel]

Feel free to open a PR, @beojan. I'm leery of adding additional dependencies to Boost, but I'd like to see what you have.

[greenc-FNAL]

Feel free to open a PR, @beojan. I'm leery of adding additional dependencies to Boost, but I'd like to see what you have.

At least since it's metaprogramming it won't be a new library dependency/new variant requirement.

[greenc-FNAL]

At least since it's metaprogramming it won't be a new library dependency/new variant requirement.

Having said that, I'd really like us to lean into modern concepts/constraints, so I'd be wary of anything that holds us back from that.