Beta: move first paragraph in lead section before infobox(es)

In order for a paragraph to be moved the following conditions must be met:

• the lead section contains at least one infobox;
• the paragraph doesn't already appear before the first infobox if any in the DOM;
• the paragraph contains text content, e.g. no <p></p>;
• the paragraph doesn't contain coordinates, i.e. span#coordinates.

The feature is feature flagged and is enabled in beta only. The change
does not affect the mobile API.

Bug: T145216
Change-Id: I199685e20bf7ed909c905d08c8ccefcf4aa3e2ab