ImagePage: Make metadata table's initial collapse CSS-only
Make the initial collapse of the metadata table not depend on
footprint once compat can be removed.
- Move the 'display: none;' styles from metadata.css to filepage.css so that they are part of the base styles for file pages (metadata.css is only for supporting metadata.js, which is loaded dynamically).
- Restrict hide-styles to only apply under .client-js to make sure the rows remain visible in no-js mode.
- Declare dependency between metadata.js and filepage.css. This is just for documentation purposes, as they are both already separately loaded on all file pages.