Rework segment_vf_collection

[benkiel]

Description

Relates to issue #4964

Current WIP, to see if adding the familyname bit to testable.Font is acceptible.

Checklist

• update CHANGELOG.md
• wait for the tests to pass
• request a review

[benkiel]

@felipesanches WIP for intital review. In my test setup, somehow this is still a bit screwy, as it's telling me that there is no matching roman for a set of fonts that 100% does, have the same family name, is getting the right value to check_STAT_ital_axis so I think it might be a cache issue. Need to set this down for now, please feel free to pick up

[benkiel]

@felipesanches I figured out the error: somewhere familyname is in the namespace after testable, and it is based on the file name. Changed familyname to family to match style in testable.Font and things work as expected in my test case.