Create builder methods for VA spec objects

### Feature description

Write functions to generate VA-Spec objects associated with common community frameworks.

### Use case

Implementers want an easy way to spin out evidence from common community frameworks to build VA Spec objects–simplifying what they need to learn and get started for common cases.

### Proposed solution

Create a new `extras.builders` package with specific modules containing evidence codes, classifications, and evidence items from common frameworks (such as those specified in our models) populating fields in the way we would expect. These modules would use our existing pydantic models for these frameworks to ensure consistency.

### Alternatives considered

_No response_

### Implementation details

_No response_

### Potential Impact

_No response_

### Additional context

_No response_

### Contribution

Yes, I can create a PR for this feature.