[bug#63604] Branch "tex-team-next" in need of review

[Nicolas Goaziou <mail@nicolasgoaziou.fr>]

Here's another update for tex-team-next branch.

The biggest change is the removal of `texlive-base' and
`texlive-latex-base' packages, which do not exist as TeX Live packages.
They are replaced by, respectively, `texlive-scheme-basic' and
`texlive-latex-bin'.

Consequently, the `#:texlive-latex-base' argument no longer exists. It
is replaced by `#:texlive-latex-bin?'. The importer automatically set it
to #f when necessary.

I also started to introduce collections and schemes from TeX Live.  At
this point, the following command,

  ./pre-inst-env guix shell --pure texlive-scheme-basic texlive-babel-french -- latex /tmp/test.tex

can compile the following LaTeX document without any hyphenation warning:

--8<---------------cut here---------------start------------->8---
\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[french]{babel}
\begin{document}
Success!
\end{document}
--8<---------------cut here---------------end--------------->8---

> So, what's next?
>
> - Install executables (copied from `texlive-bin') along with the texlive
>   package, when appropriate. The more packages you install, the less you
>   need `texlive-bin'. Ultimately, I want to get rid of `texlive-bin' as
>   a native input for every package. I think it should be limited to the
>   first few packages needed to build the rest. If that works, the
>   #:texlive-bin keyword can go away.

I admit that plan failed. Many binaries are tightly bound to each other.
I couldn't extract each of them and associate them to the right package.

It would be possible, however, to split `texlive-bin' into multiple
independent outputs (as NixOS does) in order to reduce the size of TeX
Live packages. Regarding that size, there's also the issue (at least it
seems to me) that `texlive-bin' retains a reference to GCC.

I won't look into any of the above in the current "tex-team-next"
branch.

> - Replace `texlive-latex-base', which doesn't exist in TeX Live, with
>   `texlive-latex-bin'.  Consequently, `#:texlive-latex-base' would be
>   renamed `#:texlive-latex-bin'.

Done.

> - Limit propagated inputs to the bare minimum, as defined in Tex Live,
>   and, at the same time, introduce collections and schemes. For example,
>   `texlive-scheme-basic' would replace `texlive-base'.

I started this. Since I need to review each package to reduce propagated
inputs, I may as well consider updating TeX Live to a more recent
release first. I'll see if I can do this during the next days.
Unfortunately, building `texlive-bin' takes a long time.

Feedback welcome.

Regards,