[TableListView] Add option to render metadata + bulk actions in header

[sebelga]

As part of the work the improve UX for the in Kibana (the page rendering the list of dashboards, visualisations, maps) we want to render a "selection info" bar on top of the <EuiBasicTable /> with the following functionalities

• Display how many items are being viewed (e.g. "Showing 1-10 of 45 Dashboards")
• Once one or multiple items are selected
  • Render a context menu to process bulk actions on the items
  • Render a button to select all the visible items in the table
  • Render a button to clear the selection

Design

Bulk actions

Blockers

We won't be able to have the following bulk actions:

• tag (blocked by [SavedObjectTagging] Expose flyout to assign tags to a SO #143746)
• export all (blocked by [Discuss] Expose import & export APIs for saved object  #143745)

This issue will then be completed without those 2 actions that will be added once the required APIs and components are available.

[mdefazio]

A few comments for discussion as I've been adding this to designs. Primarily for the top meta data / bulk selection, not the bottom bar:

1. Including the name of the things in the selection meta data (1-10 *Dashboards*) in the table doesn't scale well IMO. It adds potentially long text that isn't very useful to the user and would suggest we simply don't include that. I think a similar argument could be made for 'Showing' as well.
2. Wondering if the 'Select all X' option should only show if all items are selected on the page. Seems too early to show this option to the user—unlikely (again, opinion) after selecting 3 items, I'd immediately want to jump to selecting 99. Would imagine the typical flow for this would be to select all on the page, then select all across all pages.
3. This one might be unpopular, but I would like to see these buttons be at least our small size, and potentially the default style. The bottom bar will provide a larger target for these, but that is also potentially far away (and maybe not noticeable?) from where my cursor would be. So increasing the size of the buttons above the table will also make it easier, and closer.
4. I believe we currently have 'Clear selection' in the 'X selected' dropdown in Discover. It would be interesting to see what kind of interaction we see there.

My goal for these changes is to get a clear visible target when selecting several items. We previously had a large colored button that would appear before the search bar when you selected items. Switching to this provides more options, but I think makes it harder/slower to reach the primary action.