New LaTeX3 implementation

[asarhaddon]

It requires two cosmetic changes to existing tests.

[asarhaddon]

I cannot remember exactly, but I spent at least a week in cumulated time. I was expecting a challenge. LaTeX3 is an effort to make TeX/LaTeX as consistent as possible, despite its original design (Knuth did explicitly not want TeX to be Turing-complete). The recommend way to implement LaTeX extensions is to use the embedded LUA interpreter. That said, the LaTeX3 documentation is wonderful and clearly describes its purpose and limitations. I cannot reproduce the issue locally. On my machine the texlive-latex-base package is at version 2024.20240706-1, while the version in the build logs is 2019-*. I will try to require ubuntu:24.04 instead of 20.04 in the Dockerfile.

[kanaka]

Guess the latex in 20.04 was just too old.