Solving problems on the bundle level, and quicker TeX Live updates

[vlasakm]

With the great changes merged by @rm-dr recently (Thanks for the great effort!), if I understand correctly, we are in much better place with regards to being able to create new bundles from new TeX Live releases, and also patching CTAN packages on the bundle level is much easier.

I think we have a lot of open issues that are in these two categories:

1. We are too late behind TeX Live, and fixes which are already upstream, are not yet in Tectonic.
2. Something doesn't work only in Tectonic, and would be too hard to fix in upstream, but can be worked around in bundle with a patch.

I propose:

1. Create new Github issue labels along the lines will-be-solved-with-next-bundle and needs-bundle-patch. This will make us able to track all the issues that fall into the two categories outlined above.
2. Start being more quick with adopting new TeX Live releases, and start patching the bundles more often, in order to be able to fix issues and not require users to wait years or pollute their documents with ugly Tectonic-specific workarounds.

Some examples:

1. Large amount of warnings when setting font (re-opening closed issue 819) #924 - upstream agreed that we are right, and fixed the issues, but still it's years before Tectonic users see the issue solved on not every CTAN package author will fix their package.
2. Add support for pdfx #838 - pdfx package was years without upstream update and with an issue that affected xelatex / Tectonic only. The problem was fixed in upstream in July. However it will only get to TeX Live 2025 in March, and if we keep 2 years behind TeX Live releases, it will be 2027 before users see any fix.
3. Try to see if system fonts can be found in the active bundles #9 - "font names" lookup problems, are especially problematic when users use CTAN packages that use font names instead of font file names. We should probably have a better fix eventually, but fixing the packages in the bundle is already a possibility, and IIRC something we already did for fithesis-mu.

@pkgw @rm-dr @CraftSpider What do you think? With more bundles, there is of course a concern about hosting all the slightly different bundles, etc., but I think we should at least start discussing whether this is something we want to solve, and how.