They are split into individual commits

Remove _mathtext.Node.grow.

It has never been used, and the implementation was in fact buggy (if one
callsshrink many times beyond num_size_levels,.size would continue
to decrease while.width would not; if one then callsgrow,.size
and.width would then both increase, but get out of sync with one
another). I can't find a reference to grow() in the TeXbook or "TeX the
program" either(?)

Stop computing glyph_name, postscript_name in mathtext font handling.

None of the MathtextBackends actually accesses these attributes anymore,
and they are the only public API that can interact with the glyph infos
returned by the Fonts classes (and there is no public API to register
new MathtextBackends).

Remove Fonts.{set_canvas_size,width,height,descent,get_results}.

We can just inline the calls directly to the backend itself at the sole
use site (in _parse_cached). The width, height, and depth attributes on
Fonts are never used either.

Remove used_characters tracking in mathtext.

Backends that need to track what characters have been used (pdf/ps, for
subsetting purposes) already have their own logic to do so, so don't do
it in mathtext as well.

Changes in Fonts are only touching private API.

Changes in the call signature of MathtextBackendAgg/MathtextBackendPath
look like they are touching public API, but it is in fact impossible for
an external user to construct a validbox parameter (this requires
classes defined in_mathtext), soget_results is effectively private
API from a caller PoV. It is also impossible to register new
MathtextBackends without touching private API.

Thus, the only difference is in the tuple returned by
MathtextBackendAgg, which now has one fewer element. Because the return
value is a tuple which is unpacked at the call site, it is not possible
to emit a proper deprecation warning (one would need to know whether the
result is being unpacked to 6 or 7 values). Callers can work around
this by e.g. unpacking the last item into*_. Note that because this
is only for MathtextBackendAgg (i.e., a raster backend), it is unlikely
that callers actually care about the used_characters info at all.

Expire rename_parameter in _mathtext.

Lift Parser.State to toplevel as standalone class.

It doesn't need to be a nested class.

Remove now unused StandardPsFonts, latex_to_{standard,cmex}, use_cmex.

Remove unused SubSuperCluster.

PR Summary

PR Checklist

Tests and Styling

• Has pytest style unit tests (andpytest passes).
• IsFlake 8 compliant (installflake8-docstrings and runflake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry indoc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented indoc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs shouldbuild without error).