c6dd32da697e5a8052cbabe8c7605d27c43a8dfb qt: Replace obsolete functions of QDesktopWidget (Hennadii Stepanov)
1260ecd812e35185898fd555ad3e01d019072bcf qt: Add TextWidth() wrapper (Hennadii Stepanov)
Pull request description:
The following functions are obsolete in Qt 5.13:
- [`QFontMetrics::width()`](https://doc.qt.io/qt-5/qfontmetrics-obsolete.html#width)
- [`QDesktopWidget::availableGeometry()`](https://doc.qt.io/qt-5/qdesktopwidget-obsolete.html#availableGeometry)
- [`QDesktopWidget::screenGeometry()`](https://doc.qt.io/qt-5/qdesktopwidget-obsolete.html#screenGeometry)
This PR replaces them and does not change behavior.
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This is a backport from Core PR16701