For flex items with an aspect-ratio, the expectation is that the stretched
cross-sizes can be transferred to the main axis, affecting their intrinsic
inline-size contribution to the flex container's intrinsic inline-size.
Add `aspect-ratio-intrinsic-size-008.html` (adapted from 003.html) to test a
flex item with border and padding since the existing tests do not cover this.
Differential Revision: https://phabricator.services.mozilla.com/D222050
15b4507787