When using WP_Query's `"fields" => "ids"` (or `"fields" => "id=>parent"`), the returned values should be an array of integers, not array of integers represented by strings.

Adds unit tests. All other unit tests pass.

Props danielbachhuber.
Fixes #27252.


Built from https://develop.svn.wordpress.org/trunk@27686


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Media manager: Avoid a blank modal when an invalid image size class is set on the image.

props gcorne.
fixes #24409.

Built from https://develop.svn.wordpress.org/trunk@27687


git-svn-id: http://core.svn.wordpress.org/trunk@27526 1a063a9b-81f0-0310-95a4-ce76da25c4cd