drm/vmwgfx: Implement virtual kms

By default vmwgfx doesn't support vblanking or crc generation which
makes it impossible to use various IGT tests to validate vmwgfx.
Implement virtual kernel mode setting, which is mainly related to
simulated vblank support.

Code is very similar to amd's vkms and the vkms module itself, except
that it's integrated with vmwgfx three different output technologies -
legacy, screen object and screen targets.

Make IGT's kms_vblank pass on vmwgfx and allows a lot of other IGT
tests to run with vmwgfx.

Support for vkms needs to be manually enabled by adding:
guestinfo.vmwgfx.vkms_enable = "TRUE"
somewhere in the vmx file, otherwise it's off by default.

Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Acked-by: Martin Krastev <martin.krastev@broadcom.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240412025511.78553-2-zack.rusin@broadcom.com