--[BUGFIX] - Revert markerset subconfig removals; Don't write empty configs to file

[jturner65]

Removing the markerset subconfigs when they were empty caused memory corruption in certain rare cases (python variables retaining possession of a removed variable), so the change introduced in this PR is being reverted;

Instead, a subconfig with no values in its entire subconfig hierarchy (all of its own subconfigs and so on, instead of just in its own primary map) will not be written to JSON.

Motivation and Context

How Has This Been Tested

Locally c++ and python tests. Also verified with python app that fix works.

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[0mdc]

LGTM!