Ttfautohint-py

Updated embedded ttfautohint library to 1.8.2.

Updated freetype to 2.9.1 and harfbuzz to 1.8.2

Updated embedded FreeType library to 2.9.0.

- Updated embedded libttfautohint to version 1.8.1.
- Added three new keyword arguments to `ttfautohint` function: `gray_stem_width_mode`, `gdi_cleartype_stem_width_mode` and `dw_cleartype_stem_width_mode`.
These take a `StemWidthMode` enum or an equivalent integer value:
`StemWidthMode.NATURAL` (-1), `StemWidthMode.QUANTIZED` (0) and `StemWidthMode.STRONG` (1).
Check ttfautohint docs for more info on the meanings of these modes.
- Added new command line option `-a, --stem-width-mode` which takes a string of three letters with possible values 'n' for natural, 'q' for quantized, and 's' for strong (default: qsq).
This replaces the `-w, --strong-stem-width` option, which is now deprecated, though it will continue to work for a while.
- We now use `setuptools_scm` to compute the version string from git metadata.

* Fixed insert_suffix when the family_name is not a substring.
* Added tests and coverage report.