Record ghost paths for `kmod`

[ikeycode]

TLDR when we update a kernel the live VFS "forgets" the old, running kernel. This is partially resolved in Serpent OS by baking vfat into the linux-desktop kernel ensuring that we can always mount ESP & XBOOTLDR.

However for peripherals and general XHCI-land, we still rely on _request_module -> /sbin/depmod interplay. To that end we'll make moss record the ghosted paths of transaction kernel trees under /run which redirect to /.moss/root/$TX/usr/lib/modules/$VERSION. These shortlived redirects will keep hotplugging working until reboot, upon which the tmpfs /run is lost and all redirects are forgotten / unnecessary.