Minor cleanup of testing framework code

[kidder]

Proposed changes

Small changes aimed at reducing code complexity in order to improve compile time and reduce code coupling.

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

[nilsvu]

Did you intend to actually make the dependence on Charm PRIVATE in this file as the commit message promises? If so I think it would be good to also add a comment there why you made it private so it won't accidentally be made public again later.

[kidder]

I did, but I couldn't get it to work because we still have some cyclic library dependencies. I'll remove the comment from the commit message

[nilsvu]

Do you understand the cyclic dependency? How can making a dependency private introduce a cyclic dependency?

[kidder]

@nilsvu any other comments or requested changes?

[nilsvu]

LGTM