vt(4): Use vt_fb_drawrect() and vt_fb_setpixel() in all vt_fb-derivative

Review:		https://reviews.freebsd.org/D789
Reviewed by:	nwhitehorn
Approved by:	nwhitehorn
MFC after:	2 days


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271684 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f