Fontmake

- Improve compatibility checker (1052).
- Bumped minimum dependencies:
* fonttools >= 4.47.2
* glyphsLib >= 6.6.1
- Pinned ufo2ft >=2.33.4, < 3 in view of upcoming major update that will change compilation of variable OpenType Layout tables, so one can revert to this stable fontmake version if any undesired effects arise.

- Fixed ``ufo_structure`` incorrectly defaults to ``None`` (should be "package") in ``run_from_glyphs()`` method (1024, 1025).

- Added --glyph-data option to pass custom GlyphData XML files to glyphsLib (1016, 245)
- Removed MutatorMath integration, as it no longer supported for reading/writing designspaces.
If you want to continue using MutatorMath-only features such as extrapolation or anisotropic locations you can use ufoProcessor to create instance UFOs and then compile them with fontmake (834, 1019).
- Don't save master/instance UFOs to disk by default unless explicitly requested via ``-o ufo``. This means fontmake will no longer automatically leave behind itself temporary build byproducts such as "master_ufo" or "instance_ufo" in the current directory, but will only build what requested in -o option.
Plus, when the _only_ output is ufo, the ``--output-dir`` option can also be used to specify where to save the master/instance UFOs; and ``--output-path`` can be used when one specific instance UFO is built via ``-i {instance.name}`` (1020).
- Added support for building from/exporting to ufoLib2's UFO JSON format, an experimental, unofficial method to serialize a UFO in a single json file. The old ``--save-ufo-as-zip`` option is deprecated and replaced with a new ``--ufo-structure`` that can be 'package' (the default .ufo directory), 'zip' (.ufoz) or 'json' (.ufo.json) (1017).
Also added an ``--indent-json`` option to dump JSON with 2-space indentation over multiple lines. By default, ``--ufo-structure=json`` dumps the whole font as single line, no indentation.
- Added 'repacker' to the extras, enables fonttools with HarfBuzz repacker support for better/faster serialization of GPOS and GSUB table, requires ``uharfbuzz`` (44f866e).
- Added ``--ttf-curves`` option to support building ``glyf`` v1 containing cubic Bezier curves, as being proposed in https://github.com/harfbuzz/boring-expansion-spec/blob/main/glyf1.md.
The option controls whether cu2qu is run or not, and whether all cubics are converted to quadratic (default), or only when more economical to do so ('mixed') (1021).
- Bumped minimum requirements:
* fonttools >= 4.42.0

- Require glyphsLib>=6.2.5, for details see https://github.com/googlefonts/glyphsLib/releases.

- [fontmake.instantiator] Allow the default DS source to load glyph data from a non-default UFO layer (980).
- Dropped support for Python 3.7 which reached end of life, we now require Python 3.8 or greater.
- Added ``--no-auto-use-my-metrics`` option to disable setting USE_MY_METRICS component flags automatically in ufo2ft (994).
- Added option to ``--drop-implied-oncurves`` to omit on-curve points that can be implied in TrueType contours, saves a few bytes on the glyf table size (1005).
- Require:
* fonttools >= 4.40.0
* ufo2ft >= 2.32.0
* glyphsLib >= 6.2.1
* ufoLib2 >= 0.14.0

- Implement support for 'Remove Glyphs' custom parameter (958).
- [fontmake.instantiator] Use fontMath 'strict' mode to interpolate UFO glyphs to preserve geometry when off curve points coincide with on-curve points (961, 962).