[FEATURE REQ] Mock parameter objects to properly parse templates with missing parameters

### Please describe the feature or suggestion.

If a template references an object's properties when passed as a parameter but does not specify a default value for the object and there's not a parameter file available, then template-analyzer can run into parsing issues with the mock object as it won't have the expected properties.

This can later result in undesirable exceptions that could be confusing to users as some fields that reference the missing object fail to evaluate.

### Additional context

Related to #296, specifically this would address [Johnathon's comment](https://github.com/Azure/template-analyzer/issues/296#issuecomment-1292461720) in that issue.