Ship syslinux binary in the ISO filesystem

bugfix/7345-upgrade-from-iso-from-1.0-to-1.1 was merged already, this ticket is here only to help tracking what’s left to be done.

Feature Branch: bugfix/7345-upgrade-from-iso-from-1.0-to-1.1

Original created by @intrigeri on 7456 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information