Responsive images: fix the check whether the attachment meta matches the image...

Responsive images: fix the check whether the attachment meta matches the image src to work with http/https and CDNs.

Props webaware, joemcgill, azaozz.
Fixes #35045 and #35102 for trunk.
Built from https://develop.svn.wordpress.org/trunk@36121


git-svn-id: https://core.svn.wordpress.org/trunk@36087 1a063a9b-81f0-0310-95a4-ce76da25c4cd