list-base: Set view longpress to GTK_PHASE_CAPTURE

There's an issue with how GtkGestureLongPress functions where if the gesture is in phase BUBBLE and another gesture in CAPTURE claims the sequence, the prior LongPress will emit a ::pressed event regardless. More specifically, our code doesn't work because the drag gesture in GtkListBase (which tracks if rubberband should be stopped) prevent events from being sent to our view long press gesture. This makes the background menu pop-up unexpectedly while dragging on a touchscreen.