This removes the slant/italic variable axis and breaks up the font in two: roman and italic. This change will allow diverging designs for italic (for example single-storey a). It also addresses the fact that most software, including web browsers, doesn't handle VFs with slnt or ital well.
- UPM is adjusted to 2048
- Additional opsz VF axis (multi master) added which will eventually replace the separate Display family
- New tooling that uses fontmake instead of Inter's own fontbuild toolchain. (The old toolchain is still supported, i.e. `make -f Makefile_v1.make ...`)
