Move KVM demo image document from 02_Building_AGL_Image to 03_Build_and_Boot_guide_Pr...

Move KVM demo image document from 02_Building_AGL_Image to 03_Build_and_Boot_guide_Profile

Existing 02_Building_AGL_Image section is big. That include build
procedure for basic IVI demo images.  The 22_Available_KVM_Demo_Images
is a extra demo image build procedure.
These extra procedure stay on 03_Build_and_Boot_guide_Profile,
that is more better solution to avoid complexity for
02_Building_AGL_Image section.

This change move KVM demo image document from
02_Building_AGL_Image to 03_Build_and_Boot_guide_Profile.

Bug-AGL: SPEC-5247

Change-Id: I694b650438c24f47dd5212a86363d8fd1fa24749
Signed-off-by: Naoto Yamaguchi <naoto.yamaguchi@aisin.co.jp>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/documentation/+/30299
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>