Improve interface for transport model surrogates that provide fluxes

[theo-brown]

• Refactor to separate Quasilinear from QuaLiKiz
  • Lead: @hamelphi
  • PR: Generalize make_core_transport for quasilinear models. #478 Refactor runtime parameters for transport models. #479 Refactor utils into transport model classes. #485
  • Tasks:
    • Make make_core_transport and QuasilinearInputs generic
    • Separate RuntimeParams and DynamicRuntimeParams
• Utils for TGLF
  • Lead: @theo-brown
  • PR: [WIP] Add TGLF transport models and surrogates #477
• TGLF wrapper
  • Lead: @lorenzozanisi
  • Tasks:
    • RuntimeParams and DynamicRuntimeParams
    • TransportModel class
• TGLFNN wrapper
  • Lead: @theo-brown
• Miscellaneous clean-ups (Quasilinear model refactoring #497)
• Move standard computations from qualikiz_inputs to physics, improve generality and clean up existing physics @jcitrin (Clean up physics. #490)
• make_core_transport should depend on a user-specified reference length, rather than Rmaj/Rmin - @jcitrin (Generalize the transport_model _make_core_transport method. #498)

Discussed in #455

[theo-brown]

Closing as most of the issues/PRs to do with the interface are now complete. Remaining work is TGLF-specific (see #477).