3088: add full text field for licenses to default syft-json output

[spiffcs]

Description

This PR updates the syft License model to include a new FullText field without any breaking changes to the current license behavior. We select candidates for this new field based on if the metadata being analyzed contains any new line characters. Because we still want Value to be populated as it is a required field I've included a default string that will be added here when FullText is the selected outcome for a newly constructed license.

• Fixes syft extract the full description of the license in python #3088, Partial Extract full license text #2724 (next step here is adding Scan Code DB to match full text against)

Verification

Use the following Dockerfile and build a test image
docker build -t syft-3088:latest .

# Use the official Python 3.9 image from Docker Hub
FROM python:3.9

# Set the working directory in the container
WORKDIR /app

# Install the specific version of NumPy
RUN pip install numpy==1.26.4

# Specify the command to run on container start
CMD ["python"]

Run the latest syft against this image using this branch:
go run cmd/syft/main.go -o json syft-3088 | jq '.artifacts[] | select(.name=="numpy") | { name: .name, licenses: .licenses }'

The large license value extracted from the package should now be listed under the field fullText with value being set to FullText to keep the field required and not incur any breaking changes.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist:

• I have added unit tests that cover changed behavior
• I have tested my code in common scenarios and confirmed there are no regressions
• I have added comments to my code, particularly in hard-to-understand sections