Hello. When search encounters an unknown filesystem or filesystem
without partition it triggers fs module autoload which takes
noticeable time. To improve the situation I propose (after discussing
with Robert Millan) to first search without autoloading modules if we
need to find only one device (with --set ) and retry with autoloading
if without autoloading the search failed. Additionally I modify
grub-mkconfig to load correct module manually before issuing search to
decrease booting time if filesystem is different that our boot one.