[applets/weather] Port weather station picker to QQC2+ListView

Summary:
This fixes the bug I introduced when I fixed 414442 in the wrong way, makes the UI more
recular, removes a QQC1 dep, and makes the view fully keyboard-navigeable.

BUG: 414442
FIXED-IN: 5.18.0

Test Plan: {F7881687}

Reviewers: #vdg, #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: fvogt, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26640