Add onAnimationStart and onAnimationEnd to the popover

we don't have a way to know when the popover is animating or not, we should have the same api/aproach as we are doing it with our modals.

https://github.com/acl-services/paprika/pull/350#discussion_r359051966

Locate the popover component source and the modal component source to compare lifecycle handling. Inspect how modal currently provides onAnimationStart/onAnimationEnd, then add equivalent popover API/prop behavior and align any type or export updates. Run any popover tests or component examples for this package (if available), and consider it done when both callbacks exist and are emitted at animation start and end.

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