QQuickAbstractButton ignores SH_ToolButtonStyle

Private class hardcodes display to TextBesideIcon and the style appears to never change it from that to SH_ToolButtonStyle. As a result the platform theme hint (when available - as is the case on e.g. KDE Plasma) is ignored.

```
QQuickAbstractButton::Display display = QQuickAbstractButton::TextBesideIcon;

```

// SPDX-License-Identifier: BSD-2-Clause
// SPDX-FileCopyrightText: 2023 Harald Sitter <sitter@kde.org>

import QtQuick 2.15
import QtQuick.Controls 2.15

ToolButton {
    width: 100
    height: width
    action: Action {
        text: "meow"
        icon.name: "window-close"
    }
}