Move `doomdirs/example/` to just `doomdir/`, and rename the package
using it from `doom-example` to `doom-emacs`.
I do not expect to need multiple doomdirs checked in again, and I can
unclutter the packages provided by the flake a bit now that most of them
are checks.
I knew this might cause problems at some point, but it came to a head
sooner than expected: it triggered
https://github.com/magit/magit/issues/5131 (magit is pinned but
magit-section was not, and those packages expect to be kept in sync).
The fix is messier than I'd like but at least fixes magit.
This unsets DOOMPROFILE from inside the profile loader, which should
result in Doom behaving as if we were not using profiles at all.
I'm marking this experimental in part because it feels like a hack, and
in part because this is not sufficient to fix `doom doctor`.
