Make cancel animation work from JS thread.

[kmagiera]

Description

Update implementation of cancelAnimation to make it work from both UI and JS threads. Before this change, cancelling animation would only work from UI thread. Now, we use a simple trick of assigning the current (static) value to the shared value which results in the animation being cancelled.

Changes

This PR updates the implementation of cancelAniamtion to make the provided sharedValue reassign its .value prop to its current .value. This results in the animation (if it is running on the shared value) to stop at the current point. This change isn't ideal as it may have a side-effect of triggering mappers that depend on the provided value. The previous implementation wouldn't trigger mapper updates as it wasn't modifying the .value prop but only some underlying animation-related data kept in the shared value object. I think, however, this side-effect shouldn't be critical and we don't really have enough usecases for cancelAnimation to be able to tell if this causes any problems.

Testing

I tested this by extending the number of loops in WobbleExample to 70. Then I added a button that'd call cancelAnimation on rotation SV. I also tried wrapping that call with runOnUI to verify it works on both threads.

[kmagiera]

Also cc @wcandillon who pointed out this issue.

[wcandillon]

yes that works 🙌🏻