[BITV/A11Y] ActionMenu accessibility

[PVince81]

• [ ] Menu opening button does not need aria-haspopup because it is not a role="menu", but a hasmenu, and is deprecated. Can be removed because we have aria-expanded
• [ ] Menu should be inserted in the DOM directly behind the button itself → this would also fix the bug where in the files list on scrolling, the menu scrolls away.
• [ ] aria-label property is not needed as there is a text label already, can be removed.
• [ ] Focus should initially stay on the toggle button, not move into first entry of the list
• [ ] Focus should not loop through the menu but after last entry, close the menu and move to next
• [ ] Same with Shift-Tab, should move back to toggle button after first entry
• [ ] Focus needs to get border