Improve brevity of Special:MovePage form and its description
- Remove the fake "Move page:" field in the form, the page name is already shown in the <h1> title.
- Move the information that "This page has a talk page..." next to the checkbox it affects, hidden behind a clickable help icon.
INCLUDES FOLLOWUP: a1ed9acbb099440528976d677489727428fa5482,
which undoes some unnecessary message changes.