Fixes#8483, fixes#2991
With this change, `font.face.getMetrics` is now infallible, and real
bitmap fonts are properly handled and can be configured as the primary
font (or used as fallbacks), as long as the backend (FreeType or
CoreText) knows how to interpret them, since we now fall back on the
backend for any metrics we can't extract from sfnt tables (which means
we don't need any to be present in the first place).
Also, doing this uncovered a double-free issue in our FreeType
`renderGlyph` code, which thankfully wasn't too hard to track down and
fix.
> [!NOTE]
> We should vendor a true bitmap font in each of the native formats
supported by each backend and add tests for the metrics being computed
right and the glyphs being rendered correctly. Idk if we wanna block
this PR on that or not.
e2504d9cbf