use enabled:true/false in config, do not comment out

We have dictionaries of stuff that describe things that need to be present. For example:

https://github.com/dell/omnia/blob/issue-4849-omnia-modernization/src/repo_manager/input/repo_manager_config.yml#L175

If we want to omit something from that dictionary there are at least two options:

1. comment it out.
2. add a `enabled: true|false` attribute.
3. both.

I am in favor of 2. Having an `enabled: true|false`:
+ it has a consistent user experience.
+ some markup does not have a native 'comment' character (json).
+ we can write tests that ignore the `enabled` attribute to improve test coverage.
+ we can write tools that manipulate the `enabled` attribute.
+ commenting out is also an option for most cases, so if we do 2. we also get 1. and 3. in most cases.

There is an issue however: we need additional business logic to test the presence of this flag. We may wish to add a default value for when `enabled` is absent?

Start with the referenced src/repo_manager/input/repo_manager_config.yml entry and trace how configuration dictionaries are loaded and checked. Determine the intended default when enabled is absent, then identify the affected validation and coverage tests; done means enabled entries and omitted entries have documented, tested behavior.

Written by the indexing model from the issue text.