fix fork json encoding issues

[pnickolov]

Description

The JSON encoder, by default:

• outputs compact, unindented json
• escapes HTML characters

Both issues were affecting objects files that were modified by fork; the latter issue was affecting any manifest updates (fork, bump, etc.), visible on isolated solutions that have & in values.

This commit fixes both issues.

Type of Change

• Bug Fix
• New Feature
• Breaking Change
• Refactor
• Documentation
• Other (please describe)

Checklist

• I have read the contributing guidelines
• Existing issues have been referenced (where applicable)
• I have verified this change is not present in other open pull requests
• Functionality is documented
• All code style checks pass
• New code contribution is covered by automated tests
• All new and existing tests pass