More informative nested loading logging

[dginev]

Motivating example from converting a paper using expl3, which takes a good deal of time to load through each piece of the library, thus letting me see this message clearly and get a screenshot:

We seem to be 8 (eight) \input levels down from the main call, if I am reading this correctly? I think we could log this a little bit better at the STDERR spinner side of things. Not sure how...

One sample brainstorming idea would be:

| Digesting (depth 7) > Processing definitions /usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3-code.tex

And while I am making suggesting, we could also consider adding the name of the file up front, to avoid always having to follow the long paths. As in:

| Digesting expl3-code.tex (depth 7) > Processing definitions /usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3-code.tex

Maybe even a quieter, minimal variant is workable:

| Digesting expl3-code.tex (depth 7)

unsure what's best, but I think there's some easy upgrade out there that makes expl3-code.tex loading readable :>

[dginev]

Maybe to piggyback on this issue instead of avoiding a new one: Now that I am starved for free HDD space for arXiv, I've started to examine what large files get added, and indeed found a .log file larger than 1 GB. It was for article 1803.06011 and contains 10,461,496 lines of logging messages.

The vast majority of those are of the form:

Warning:expected:<number> Missing number, treated as zero
        at A_UNIFIED_THEORY_OF_REGRESSION_ADJUSTMENT_v18.tex; line 2381 col 0 - line 2381 col 12
        while processing \numexpr
        Next token is T_CS[\prooftoks] ( == Core::Definition::Constructor[\prooftoks]) more: +\count@\relax\ifnum\count@<\value{proofcount}\advance\count@\@ne\relax\expandafter\iterate\fi\let\iterate\relax
        In Core::Gullet[@0x5596554b4d28] /dev/shm/H7anTVr_Wr/A_UNIFIED_THEORY_OF_REGRESSION_ADJUSTMENT_v18.tex; from line 2381 col 0 to line 2381 col 12

which continues on that line until my iflimit guard is reached:

Fatal:timeout:if_limit Conditional limit of 699999 exceeded, infinite loop?
        at TeX.pool.ltxml; line 747
        In Core::Definition::Conditional[\ifnum ... /usr/local/share/perl/5.32.1/LaTeXML/Package/TeX.pool.ltxml; line 747

one strange bit is that the log file wasn't compressed (that I'll investigate separately), but apart from that - I wonder if we ever need to produce more than say 100 logging messages (of any severity) from the same source line? I could also add log-trimming on the cortex side of things, a bit of a soft problem...