* Fix overscroll behaviour of `StretchingOverscrollIndicator` on directional change while scrolling

* Remove trailing spaces

* Change naming of `_StretchDirection` values to `trailing` and `leading`

* Remove trailing space

* Apply suggestions from code review

* Fix stretching overscroll indicator direction on fling

* Fix issue when changing direction while recede animation is playing

* Remove trailing space

* Add test for changing direction during recede animation