added a dummy STAT table to PartialInstancer-VF.ttx font that has all 4 AxisValue formats.
It doesn't have contain AxisValue for each fvar NamedInstance like the spec recommends, but it's ok for the sake of this test
I added an MVAR table to the PartialInstancer-VF.ttx test font with made-up deltas for
OS/2.yStrikeoutSize, post.underlinePosition and post.underlineThickness.
I defined 3 regions, one with only wght, one with only wdth, and one with both wdth and wght axes.