fix(FEC-14156): quiz overlay behind cvaa freezes

[lianbenjamin]

Description of the Changes

bugfix

Issue:
when opening the cvaa (advanced captions settings) while the video is playing and the video reaches a quiz question cue point, then closing the cvaa overlay- the quiz question overlay stays on the player and there is no way to close it.
the root cause is that closing the cvaa causes the removal of overlay-active class, which causes the odd behavior of the quiz question overlay.

Fix:

• do not remove the overlay-active class if overlayPortal component has multiple children- remove it only if there's a single child
• create a reusable getOverlayPortalElement function which returns the overlayPortal element
• use getOverlayPortalElement function in other components
• expose getOverlayPortalElement function for a future use outside of core scope

Resolves FEC-14156