knowledge-base: retract an accepted record or its clauses on the operator's Approve

The operator prefers removing a wrong decision to stacking a correcting
record on it, and withdraw took only reserved or proposed records. retract
asks the operator through the router like a record that needs the operator,
and changes nothing until the Approve; a retracted record or clause no longer
holds in ask, holds, get, links and progress, history keeps every version, and
the whole-set rules still read a retracted record's links so a retraction alone
raises no finding. withdraw with retraction true takes a waiting one back.

modules/mesh-knowledge/cmd/mesh-knowledge/progress_test.go

@@ -187,15 +187,6 @@ func TestADesignsMilestonesAreTheTrackersRecords(t *testing.T) {
 	}
 }
 
-func containsInt(xs []int, n int) bool {
-	for _, x := range xs {
-		if x == n {
-			return true
-		}
-	}
-	return false
-}
-
 // 1947/AC6: the designs are read once per commit of hq, and again when it moves; the mesh level names those with
 // milestones one by one and counts the rest.
 func TestDesignsAreReadAgainOnlyWhenHqMoves(t *testing.T) {