Add hover text to vertical ellipsis button on issue board cards

#367473 (closed) introduced a button on issue cards in issue boards.

To bring this into alignment with other ellipsis action menus and Pajamas standards:

1. Show a tooltip "Card actions" when hovering the board action button
2. Add aria-label "Card actions", which can replace the .gl-sr-only label ("Move card").

Background

It should have a hover text, for example: More actions that is already present in some places. From the docs instructions:

After adding the hover text, update the documentation steps that were added in !97094 (merged).