Gif Animation Support (#7330)

Gif Animation Support (#7330)

* Add image animation API.

* Add animated image tests.

* Add animated image UWP implementation.

* Add animated image IOS implementation.

* Add animated image Android implementation.

Also include GIF image parser base class + android parser sub class.

* Add animation finished playing event to Android/IOS for image.

* Add fallback when loading none GIF as animation image.

* Adding a couple of additional tests for animated images.

* Adjusting image animation support based on PR feedback.

* Add support to reload as animated image on StartAnimation call.

* Add UITest and activity indicator when loading from source for Issue1704.

* Reduce number of temporary bitmaps when scaling.

* Implemented review feedback.

* Animation problems related to Android API level 19 and earlier
due to a couple of bugs and changed behavior in AnimationDrawable class.
Implemented a couple of fixes and workaround related to these bugs, fixing
the animation issues on devices before Android Lollipop.

* Moved a couple of methods implemented in FormsAnimationDrawable into an
interface that is used to hide implementation details. Enables possibility
to factor different implementations of animation support going forward.

* Fixed review feedback and comments.

* Notify IOS to redraw control when changing animation layer.

* - android rebase fixes

* - first set of iOS changes for gifs

* - uwp Gif changes

* - clean up android gif code and enable gif for ImageButtons

* - cleanup iOS gif implementation

* - fix imagebutton and other sources

* - add imagebutton to tests

* - getting rid of start/stop and just using IsAnimationPlaying

* - image button

* - adding animation handler for android

* - replace gifs

* - fix rebase issues

* Added gif samples in Core Gallery

* Updated gif Core Gallery sample

* Fixed UWP gif samples path

* - remove auto play
- fix uwp so it plays correctly on load

* Added support to Url gifs on Android

* - fix rebase

* - fix NRE and iOS repeat

* - fix android loop counter

* - fix animation stopped on ios

* - fix removed ImageHandler interface Android

* - add top margin so ui tests can click button