Minor popover fixes

Currently, the selection context menu popover has an arrow, unlike the background context menu popover. This is inconsistent, so let's drop the arrow.

Moreover, both the rename popover as well as selection context menu popover when triggered from the menu key show up at an incorrect position. Fix this by altering the translation of the coordinates.

Edit: I have also added to this MR a change that fixes #2091 (closed) and another re-enables the ability to open the background context menu popover with a keyboard.

Fixes #2086 (closed)