pid1,vconsole-setup: lock /dev/console instead of the tty device

pid1,vconsole-setup: lock /dev/console instead of the tty device

As requested in https://github.com/systemd/systemd/pull/27867#pullrequestreview-1567161854.
/dev/console, /dev/tty0, and /dev/ttyN are "different" device nodes
that may point to a single underlying device. We want to use a single
lock so that we don't get a race if different writers are using a different
device path, so let's just always lock around /dev/console.
This effectively makes the locking less granular.

Fixup for a0043bfa51281c2374878e2a98cf2a3ee10fd92c.
Fixes https://github.com/systemd/systemd/issues/28721.
Maybe fixes https://github.com/systemd/systemd/issues/28778 and
https://github.com/systemd/systemd/issues/28634.