[EuiDataGrid] Header Popover does not re-compute the position in scrollable container

[ince01]

How to fix this issue? I tried adding repositionOnScroll prop but it still does not work properly

Originally posted by @ince01 in #3924 (comment)

[cee-chen]

This issue is semi-related to the comment I left in #6592 (comment) - in general EUI does not explicitly support popover repositioning on scrolling containers (as opposed to scrolling bodies), and we'll need to add extra support to our portal API to allow consumers to portal popovers into scrolling containers (which negates the need for repositionOnScroll).