Regression because of a commit 415d96da

Now lvm and cryptsetup are required not only in the
installed system, but also in altinst. This is because the remount
happens before the base system is installed.

wi-fi may also need to be configured in the installer.

This reverts commit 1076d79f.

The only workable xvt is xterm, since only works with it:

  xinit cmd

See commit: 2451a17c

Requested by Ivan A. Melnikov <iv@altlinux.org>

Use a prebuilt grub image for EFI, creating BOOT/EFI/grub.cfg

See ALT bug 31971