absolutePosition: account for possible offetParent

[jonlarsson]

The function absolutePosition is not taking offsetParent into account when calculating the absolute position of an element.

One exmple where this i causing problems is using a PrimeNG popover in a datatable . The datatable has position: relative by default which causes any nested popover to be offset by the datatable position. Since this is not accounted for in absolutePosition, the resulting position is wrong.

It is often preferrable from an accessability standpoint to keep the popover a sibling to the button that opens it.