Support `AsCollection::of($map)`, `AsCollection::using($class, $map)`

[erikn69]

Summary

Support for AsCollection::of($map), AsCollection::using($class, $map)

• Closes #1703

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update
• [ ] Misc. change (internal, infrastructure, maintenance, etc.)

Checklist

• [x] Existing tests have been adapted and/or new tests have been added
• [ ] Update the README.md
• [ ] Code style has been fixed via composer fix-style