util/slicesx: add package for generic slice functions, use

Now that we're using rand.Shuffle in a few locations, create a generic
shuffle function and use it instead. While we're at it, move the
interleaveSlices function to the same package for use.

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I0b00920e5b3eea846b6cedc30bd34d978a049fd3

net/dnscache/dnscache_test.go

@@ -141,30 +141,6 @@ func TestResolverAllHostStaticResult(t *testing.T) {
 	}
 }
 
-func TestInterleaveSlices(t *testing.T) {
-	testCases := []struct {
-		name string
-		a, b []int
-		want []int
-	}{
-		{name: "equal", a: []int{1, 3, 5}, b: []int{2, 4, 6}, want: []int{1, 2, 3, 4, 5, 6}},
-		{name: "short_b", a: []int{1, 3, 5}, b: []int{2, 4}, want: []int{1, 2, 3, 4, 5}},
-		{name: "short_a", a: []int{1, 3}, b: []int{2, 4, 6}, want: []int{1, 2, 3, 4, 6}},
-		{name: "len_1", a: []int{1}, b: []int{2, 4, 6}, want: []int{1, 2, 4, 6}},
-		{name: "nil_a", a: nil, b: []int{2, 4, 6}, want: []int{2, 4, 6}},
-		{name: "nil_all", a: nil, b: nil, want: []int{}},
-	}
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			merged := interleaveSlices(tc.a, tc.b)
-			if !reflect.DeepEqual(merged, tc.want) {
-				t.Errorf("got %v; want %v", merged, tc.want)
-			}
-		})
-	}
-}
-
 func TestShouldTryBootstrap(t *testing.T) {
 	oldDebug := debug
 	t.Cleanup(func() { debug = oldDebug })