"Select this item" isn't a good field label for screenreaders

Problem/Motivation

For users of screenreaders, the field label on every checkbox/radio button will be "Select this item", which makes it hard to distinguish which entity the are selected.

Steps to reproduce

Open a media browser, inspect the HTML and look at the <label> tag. Notice that the checkbox or radio button for every entity has a label of "Select this item".

Proposed resolution

Change the label to "Select item ENTITY_LABEL".

Remaining tasks

1. Post the patch!

User interface changes

No visible changes - only the invisible label seen by screenreaders.

API changes

No API changes.

Data model changes

No data model changes.