Ensure that AREA used by IMG is visible.

[jeeyyy]

Expectation:
The function isAreaVisible used within isVisible should consider if AREA elements are outside of view/ coordinates of the IMG that uses the AREA.

Actual:
Currently the function isAreaVisible does not consider if referenced AREA is in view of the IMG that uses it.

Motivation:
If the coordinates sets an AREA that's bigger than the IMG it's mapped on, the AREA element will be visible to assistive technologies, but not to sighted users.

Note: isAreaVisible is an enhancement to isVisible function as a part of of the rule identical-links-same-purpose. See PR & comment - #1649 (comment)