[dccd] NaN moves

[vicb]

double.NAN moves could not be detected with the current implementation (at least for Collections, Map to be checked).

The reasons are:

• DuplicateMap.remove assert(map.containsKey(record.item)) will fail for NaN,
• _DuplicateItemRecordList.get uses identical while it should use the loose test.

[vicb]

      it('should detect [NaN] moves', () {
        var list = [double.NAN];
        var record = detector..watch(list, null, null)..collectChanges();

        list..clear()..addAll(['a', double.NAN]);
        record = detector..watch(list, null, null)..collectChanges();
        expect(detector.collectChanges().moveNext()).toEqual(true);
        expect(iterator.current.currentValue, toEqualCollectionRecord(
          // ...   
        ));
      });

[vicb]

fix started in https://github.com/vicb/angular.dart/compare/0610-dccdperf