For "math into SVG" conversion, run latex+dvisvgm only once for all equations at once

As far as I understand from quick look sphinx.ext.imgmath, it executes latex and dvisvgm for each math equation when configured to produce SVG output.

It appears to be possible to execute latex only once and then dvisvgm once on the multipage document. This is made easier with standalone class on latex side.

I used for testing this latex file:

\documentclass[12pt, multi=sphinxmathenv, border=12pt]{standalone}
\begin{document}
\begin{sphinxmathenv}
  $F^{\mu\nu} = \partial^\mu A^\nu - \partial^\nu A^\mu$
\end{sphinxmathenv}
\begin{sphinxmathenv}
  \huge$F^{\mu\nu} = \partial^\mu A^\nu - \partial^\nu A^\mu$
\end{sphinxmathenv}
\end{document}

then

$ dvisvgm -p "1-" --font-format=woff temp.dvi
pre-processing DVI file (format version 2)
processing page 1
  graphic size: 102.482353pt x 9.333332pt (36.018428mm x 3.280291mm)
  output written to temp-1.svg
processing page 2
  graphic size: 218.927669pt x 20.031837pt (76.944275mm x 7.040386mm)
  output written to temp-2.svg
2 of 2 pages converted in 0.363326 seconds

This example shows that the two figures get their respective dimensions.

tested with dvisvgm 2.6.2.

Start in sphinx.ext.imgmath and reproduce the supplied standalone LaTeX document with dvisvgm. Trace how SVG output is currently generated per equation; done means processing all equations through one LaTeX run and one multipage dvisvgm run while preserving each figure's dimensions.