Standardizing boot loader entry format

{configs/releng/efiboot/loader/entries/archiso-x86_64-{cd,usb}.conf,configs/releng/syslinux/archiso_{pxe,sys}.cfg}:
Standardizing the boot loader entry format by switching all entries to the form:
"Arch Linux install medium (<CARCH>[, <PROPERTY>])".
This removes the distinction between "CD" and "USB" when booting in UEFI "el-torito" (as the information is not useful).
Changing some of the syslinux help text as well to reflect this change. This also drops the specific <CARCH> from the
syslinux help text as it is duplicated information.

Closes #24