nixos/hidpi: remove

The single option tries to do too much work, which just ends up confusing people.

So:
- don't force the console font, the kernel can figure this out as of #210205
- don't force the systemd-boot mode, it's an awkward mode that's not supported
  on most things and will break flicker-free boot
- add a separate option for the xorg cursor scaling trick and move it under the xorg namespace
- add a general `fonts.optimizeForVeryHighDPI` option that explicitly says what it does
- alias the old option to that
- don't set any of those automatically in nixos-generate-config

nixos/modules/installer/tools/nixos-generate-config.pl

@@ -518,21 +518,6 @@ EOF
     }
 }
 
-# For lack of a better way to determine it, guess whether we should use a
-# bigger font for the console from the display mode on the first
-# framebuffer. A way based on the physical size/actual DPI reported by
-# the monitor would be nice, but I don't know how to do this without X :)
-my $fb_modes_file = "/sys/class/graphics/fb0/modes";
-if (-f $fb_modes_file && -r $fb_modes_file) {
-    my $modes = read_file($fb_modes_file);
-    $modes =~ m/([0-9]+)x([0-9]+)/;
-    my $console_width = $1, my $console_height = $2;
-    if ($console_width > 1920) {
-        push @attrs, "# high-resolution display";
-        push @attrs, 'hardware.video.hidpi.enable = lib.mkDefault true;';
-    }
-}
-
 
 # Generate the hardware configuration file.