LP1803787 Grid toolbar actions menu component; cleanup

LP1803787 Grid toolbar actions menu component; cleanup

Moves the guts of the grid toolbar actions menu (the buttons) to a
dedicated component that can be shared by both the actions drop-down
menu and the actions popover.  This adds support for honoring
disableOnRow for the popover actions. And avoids duplication.

Adds a sandbox example of using the toolbar action click event and
divider.

Some minor code cleanup/consistency changes.

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>