be_get_boot_args interface implementation in libbe (loader project)
To support fast boot feature, some components are currently using grub_get_boot_args() interface from libgrubmgt library. With loader setup, such interface is no longer applicable and an alternative should be provided. As building kernel boot args is depending on information in boot environment, implementing such interface in libbe seems most reasonable approach. Note, the libbe is still illumos private, and consumers are on gate.