pkg/list/sort: always use stable sort
pkg/list/sort: always use stable sort

Change-Id: I11fd18901a1891c1fffaa93bb462a24d336792c1
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/7363
Reviewed-by: Paul Jolly <a027184a55211cd23e3f3094f1fdc728df5e0500@myitcv.org.uk>
Reviewed-by: CUE cueckoo <0f32a827c9a5f00281f936ac78b5ef3ba80a954c@gmail.com>

cuelang/cue