internal: store Body in Attr type
internal: store Body in Attr type

Change-Id: Ie0bc6d19647a9c940fd43025d6c9a9636792fb2f
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/9187
Reviewed-by: CUE cueckoo <0f32a827c9a5f00281f936ac78b5ef3ba80a954c@gmail.com>
Reviewed-by: Paul Jolly <a027184a55211cd23e3f3094f1fdc728df5e0500@myitcv.org.uk>

cuelang/cue