[TableListView] Bottom bar for bulk actions

[sebelga]

As part of the UX improvement of the <TableListView /> component we want to render a bottom bar whenever there is one or multiple items selected in the table. This will allow the user to execute the actions in bulk for multiple saved objects.

The bottom bar should

• Indicate the number of items selected
• Have buttons to tag, export and delete the selected items

Design

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.