[Woo POS] Explore and add checks for non-supported device/size-class combinations

[iamgabrielma]

Ref: p91TBi-bdN-p2#comment-12100

In iOS, if the app detects a compact horizontal size class in the POS mode, we can show a “not supported” screen to inform them to change the split screen state to get back to a regular horizontal size class.

[dangermattic]

Thanks for reporting! 👍