[DX] Add Flush all caches > Views to admin bar

Description of the need

When developing, it's a common need to flush various caches, a need that is conveniently met by the "Flush all caches" item and its submenu items in the admin bar.

Views is an exception to the convenience: The "Clear Views' cache" button is buried in the Advanced sub-tab of the Settings tab of the Views page (and if one has a lot of Views, the Settings menu item is at the bottom of the admin bar submenu, sometimes not even visible when there are long lists of Views). It would be nice to add the ability to clear the Views cache from the same submenu in the admin bar as all the other cache-clearings.

Proposed solution

Add Home > Flush all caches > Views to the admin bar if Views UI module is enabled.

It should be straightforward. The function views_ui_tools_clear_cache() does the clearing. Once would simply need to implement hook_admin_bar_cache_info(), along the lines of system_admin_bar_cache_info() or update_admin_bar_cache_info(); presumably as views_ui_admin_bar_cache_info().

Draft of feature description for Press Release (1 paragraph at most)

Backdrop now includes the ability for developers to clear the Views cache directly from the admin bar.