This changes how initial searches can be handled via config rather than
specific action so they can be considered in how the initial data load
is done, to prevent the default empty state loading and overwriting the
search data if it lands later (which was commonly likely).
For #4778
Cleaned up and updated page picker a bit, allowing longer names to show,
clicking through to item without triggering popup, and updated to use
hidden attributes instead of styles.
Added phpunit tests to cover supporting entity-selector-templates
endpoint.
