WIP: action-row: Pack actions from the start
Add the suffix box to put the action widgets in, and pack the action widgets in it from the start rather than from the end. This implies that all implementations of HdyActionRow must stop packing the actions in reverse order.
Fixes https://source.puri.sm/Librem5/libhandy/issues/88
WIP because we need https://source.puri.sm/Librem5/libhandy/merge_requests/248 first.