refactor(font): rewrite makeFF in Python
#3714
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The old version was a big list of commands to `mftrace` in a single target. Now the code uses a pattern to create the different files in a more idiomatic way. It is not necessary to explicitly state the encoding for some files. The `mftrace` script can always find the correct encoding automatically.
This list isn't necessary because we generate a bunch of fonts in the docker container, and copy everything over. This list is implicitly defined by the output of `.ff` scripts.
Rewriting `makeFF` in Python improves the code in several ways: - Increases maintainability as Python code is more readable than dense Perl code using mostly string substitutions (sometimes with regular expressions) to write scripts, and rewrite other files. - Pair kerning is a feature that requires us to read the `.tfm` files that contain those metric tables. The current codebase contains a `.tfm` parser written in Python, not in Perl. This commit makes it possible to use that to build pair kerning tables in the FontForge scripts. This new code also splits the mapping between the old TeX font codepoints and the modern Unicode scalar values into a separate module that can in the future be reused for metrics generation. This decreases code duplication, and makes changes more robust. It's also easier to write sanity checks in the new mappings to catch easy-to-miss mistakes like codepoints being mapped twice.
This was referenced Sep 17, 2022
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No behavior is changed by this PR, as the generated fonts are bit-for-bit identical, but the code that generates them is more readable.
Assumes #3713 gets merged, but I've opened the PR early to give a preview of where my work is going. This PR is ready for review, but I can rebase the code if necessary.