Pkgcore

Fix failure instantiating ``ConfiguredTree`` causing various tools based on pkgcore to fail.

**Don't use this version, it has hard breakage of consumers.**

- various fixes and refactors to code (ferringb, 428)
- add missing authors to ``pyproject.toml`` file (ferringb, 429)
- add support for ``git`` urls for sync purposes (vitaly-zdanevich, 434)

- fix: parsing bug that allows a revision to be part of a package (ferringb, 419, 420)
- fix: child repository not inheriting license groups when it defines none (ferringb, 424)
- pytest plugin: ``create_ebuild`` writes ``LICENSE`` before ``SLOT`` to match variables order of ``skel.ebuild`` (anthonyryan1, 425)
- ci: add workflows to verify ``pmaint regen`` against gentoo repository (arthurzam)

- operations.format.fetch_base: try to use proxy values from domain (i.e. ``/etc/portage/make.conf``) as first priority (arthurzam)
- metadata.xsd: add codeberg remote-id (laumann, 414)
- examples/verify_at_done: add new helper tool to collect done AT bugs (arthurzam)
- eclassdoc: many changes to the way pkgcore generates docs from eclasses: removal of ``Bugreports`` tag, display default or initial values, display exported phases, various improvements to the RST output (arthurzam, 346)
- eclassdoc: add devbook output format (arthurzam, 346)
- various code refactoring and modernization (ferringb, 415, 417)
- drop support for Python 3.9 (arthurzam)

- enable python 3.12 for pkgcore (thesamesam, 402)
- manifest: support proxy configuration (arthurzam, https://github.com/pkgcore/pkgdev/issues/103)
- ebuild.repository: add support for stabilization groups (arthurzam, 411)

- manifest: fix missing errors when all ebuilds for a package are masked as bad. This fixes a long standing bug that ``pkgdev manifest`` wasn't working without any helpful error messages when all ebuilds for a package fail to source. (zhuyifei1999, echuber2, 406)
- multiplex.tree: fix config name and type (arthurzam)
- pkgsets.glsa: exclude metadata files from warning (arthurzam)
- manifest: pass ``$PATH`` environment variable to calls of ``FETCHCOMMAND`` (arthurzam, https://github.com/pkgcore/pkgdev/issues/145)