feat(validation): handle multi model validation

[mike-winberry]

Is your feature request related to a problem? Please describe.

In order to better support the direction of lula, it may be beneficial to work on a way to handle validation for yaml files with multiple types of documents ie (component-definition and catalog, etc...), the default is failure since the oscal schema is "one-of", so the default state should remain the same, but allow for user to ignore the rule.

Describe the solution you'd like

• Given a file with more than one OscalModels
• When an validation is run
• Then user has the option to handle validation of each model individually (more than one normally would fail)

Describe alternatives you've considered

• handling in lula, this is a potential resolution, but I believe a much cleaner solution can be offered at the source as additional helper types may need generation to simplify across versioning.

[brandtkeller]

Current decision is to move away from multi-model and stick to single-model. This and the associated PR can be closed.