Remove $FreeBSD$: one-line .c comment pattern

Remove /^/[*/]\s*\$FreeBSD\$.*\n/

loader.efi: fix panic() after BS off

panic() is using multiple services - attempting to read
keyboard, accessing time functions and finally, exiting the loader.

Protect all the accessed listed above. Note, when BS are off,
we really can not just exit the loader, we only can reboot.

MFC after: 1 week

loader.efi: efi variable rework and lsefi command added

This update does add diag and debug capabilities to interpret the efi
variables, configuration and protocols (lsefi).

The side effect is that we add/update bunch of related headers.

loader.efi: add missing EFI GUIDs

These were found during bring-up on a new arm64 platform and in an
amd64 VM.

Submitted by: Arshan Khanifar <arshankhanifar_gmail.com>
Reviewed by: imp
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D14036

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix