CP-6751: Add max_resolution_{x,y} to VGPU_type

These are parsed from the NVIDIA config files in the same way as the other
parameters. The config file specifies a single string for max_resolution which
we split into its dimensions.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
CP-6751: Show max-resolution for VGPU_types on CLI

This is displayed as a single value (rather than dimensions) e.g. 1920x1200.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
Change default fields displayed for vgpu-type-list

Remove framebuffer-size in favour of max-resolution and max-heads.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>