Completes OPEN-3563 Add model property indicating if baseline / shell…

[gustavocidornelas]

… / non-shell and Closes OPEN-3616 Replace 'baseline-model' resource name in favor of common 'model' resource

Summary

• Gets rid of the baseline-model resource in the staging area. Instead, uses the common model resource name.
• Adds the modelType to the ModelSchema and BaselineModelSchema. This property indicates whether the model is a shell, baseline or full model. This is now expected by the backend (from this PR).
• Other than that, just updates the validation logic to work with the new resource names.

[linear]

OPEN-3616 Replace 'baseline-model' resource name in favor of common 'model' resource

OPEN-3563 Add model property indicating if baseline / shell / non-shell