internal/core/...: fully transition away from Vertex.VisitLeafConjuncts
These remaining cases were all simple, except value.go which can make
use of slices.SortedStableFunc, and constraints.go where we can simplify
the logic by removing a bool variable.
Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: Ieb4ec6b43fab3e027e724aabe278183ed131acce
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1224304
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>