Documentation: kvm: replace section numbers with links

In order to simplify further introduction of hyperlinks, replace explicit
section numbers with rST hyperlinks.  The section numbers could actually
be removed now, but I'm not going to do a huge change throughout the file
for an RFC...

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241023124507.280382-4-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>