pkg/adt: add "IntervalTree.Delete" failure case

Described in https://github.com/etcd-io/etcd/issues/10877.

"black-height" property: Every path from a node to any descendant leaf node must have the same number of black nodes.

Expected

    After deleting 11 (requires rebalancing):
                            [510,511]
                             /      \
                   ----------        --------------------------
                  /                                            \
              [383,384]                                       [830,831]
              /       \                                      /          \
             /         \                                    /            \
      [261,262](red)  [410,411]                     [647,648]           [899,900](red)
          /               \                              \                      /    \
         /                 \                              \                    /      \
      [82,83]           [292,293]                      [815,816](red)   [888,889]    [972,973]
            \                                                           /
             \                                                         /
          [238,239](red)                                       [953,954](red)

Got

    After deleting 11 (requires rebalancing):
                            [510,511]
                             /      \
                   ----------        --------------------------
                  /                                            \
              [82,83]                                       [830,831]
                    \                                      /          \
                     \                                    /            \
                  [383,384]                        [647,648]            [899,900]
                  /       \                              \                  /    \
                 /         \                              \                /      \
           [261,262]      [410,411]                      [815,816]   [888,889]    [972,973]
             /   \                                                                  /
            /     \                                                                /
     [238,239]   [292,293]                                                  [953,954]

This violates "black-height" property.

Signed-off-by: Gyuho Lee <leegyuho@amazon.com>

pkg/adt/interval_tree_test.go

@@ -257,6 +257,31 @@ func TestIntervalTreeDelete(t *testing.T) {
 	if deleted := tr.Delete(NewInt64Interval(11, 12)); !deleted {
 		t.Fatalf("range %v not deleted", range11)
 	}
+
+	expectedAfterDelete11 := []visitedInterval{
+		{root: NewInt64Interval(510, 511), color: black, left: NewInt64Interval(383, 384), right: NewInt64Interval(830, 831), depth: 0},
+
+		{root: NewInt64Interval(383, 384), color: black, left: NewInt64Interval(261, 262), right: NewInt64Interval(410, 411), depth: 1},
+		{root: NewInt64Interval(830, 831), color: black, left: NewInt64Interval(647, 648), right: NewInt64Interval(899, 900), depth: 1},
+
+		{root: NewInt64Interval(261, 262), color: red, left: NewInt64Interval(82, 83), right: NewInt64Interval(292, 293), depth: 2},
+		{root: NewInt64Interval(410, 411), color: black, left: newInt64EmptyInterval(), right: newInt64EmptyInterval(), depth: 2},
+		{root: NewInt64Interval(647, 648), color: black, left: newInt64EmptyInterval(), right: NewInt64Interval(815, 816), depth: 2},
+		{root: NewInt64Interval(899, 900), color: red, left: NewInt64Interval(888, 889), right: NewInt64Interval(972, 973), depth: 2},
+
+		{root: NewInt64Interval(82, 83), color: black, left: newInt64EmptyInterval(), right: NewInt64Interval(238, 239), depth: 3},
+		{root: NewInt64Interval(292, 293), color: black, left: newInt64EmptyInterval(), right: newInt64EmptyInterval(), depth: 3},
+		{root: NewInt64Interval(815, 816), color: red, left: newInt64EmptyInterval(), right: newInt64EmptyInterval(), depth: 3},
+		{root: NewInt64Interval(888, 889), color: black, left: newInt64EmptyInterval(), right: newInt64EmptyInterval(), depth: 3},
+		{root: NewInt64Interval(972, 973), color: black, left: NewInt64Interval(953, 954), right: newInt64EmptyInterval(), depth: 3},
+
+		{root: NewInt64Interval(238, 239), color: red, left: newInt64EmptyInterval(), right: newInt64EmptyInterval(), depth: 4},
+		{root: NewInt64Interval(953, 954), color: red, left: newInt64EmptyInterval(), right: newInt64EmptyInterval(), depth: 4},
+	}
+	visitsAfterDelete11 := tr.visitLevel()
+	if !reflect.DeepEqual(expectedAfterDelete11, visitsAfterDelete11) {
+		t.Fatalf("level order after deleting '11' expected %v, got %v", expectedAfterDelete11, visitsAfterDelete11)
+	}
 }
 
 func TestIntervalTreeIntersects(t *testing.T) {