search: Prevent the search box from enlarging the view

By default, the search filters widget calculates its minimumSizeHint as the sum of its components' minimum widths.

This minimum width hint will scale up the widgets hierarchy, finally imposing a minimum width to the contents view, which in certain conditions can take the space from the side panels.

Let's set a minimum width hint of 0, so it is the filters widget which always adapts to the available view size instead.

BUG: 466796 FIXED-IN: 23.04