AH rewrite: Prep control system for new AH infrastructure

[knelli2]

Proposed changes

Sixteenth PR in horizon finder changes. Includes editing RunCallbacks to conform to the new ah::protocols::Callback protocol and editing the submeasurement protocol to accept horizon metavars.

Note that none of the new AH infrastructure is used in any executables yet. This is that last PR before changing the executables to use the new infrastructure.

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments