Media Library item styles assume contextual module is present

Problem/Motivation

For media item labels to be positioned correctly, the enclosing <article> needs to be position: relative;. If the page includes the contextual module libraries then the <article> will have the .contextual-region class and be styled by this bit in contextual.module.css

.contextual-region {
    position: relative;
}

There are legit scenarios such as this one with Experience Builder where the media library is used without contextual present -- even on sites with that module enabled.

It winds up looking like this, with the labels under the images out of place (not hugely so, but still not a great look)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet