Add VT driver for VBE framebuffer device

Implement vt_vbefb to support Vesa Bios Extensions (VBE) framebuffer with VT.
vt_vbefb is built based on vt_efifb and is assuming similar data for
initialization, use MODINFOMD_VBE_FB to identify the structure vbe_fb
in kernel metadata.

struct vbe_fb, is populated by boot loader, and is passed to kernel via
metadata payload.

Differential Revision: https://reviews.freebsd.org/D27373