Adds a type check to Omega Config

[philipwjones]

Adds a data type check to Config retrievals in order to provide a clearer error message than the generic yaml-cpp message. When yaml-cpp cannot convert to the requested data type, Omega now aborts with a clear error message that includes the offending variable name.

Fixes #444

Checklist

• Documentation: Does not impact existing documentation
• Linting
  • Pre-commit run locally
• Building
  • CMake build does not produce any new warnings from changes in this PR
• Testing
  • Add a comment to the PR titled Testing with the following:
    • Which machines CTest unit tests
      have been run on and indicate that are all passing.
    • The Polaris omega_pr test suite
      has passed, using the Polaris e3sm_submodules/Omega baseline
    • Document machine(s), compiler(s), and the build path(s) used for -p for both the baseline (Polaris e3sm_submodules/Omega) and the PR build
    • Indicate "All tests passed" or document failing tests
    • Document testing used to verify the changes including any tests that are added/modified/impacted.
    • Performance related PRs: Please include a relevant PACE experiment link documenting performance before and after.

[philipwjones]

CTests pass on PM cpu and gpu. Also tested with an edited Config with bad inputs to verify appropriate error messages are generated.

[cbegeman]

@philipwjones Thanks for getting to this so quickly! I think this will be broadly helpful. Would you like me to do any additional testing?

[xylar]

Approving based on an inspection of the code. I agree, these error messages will be helpful.