Stylesheet Margin/Padding squashes QSpinBox

Since commit 96adebed606cdbc73c73778917d777dc04c6e93e, setting a margin or padding (or both) on a QSpinBox using a stylesheet squishes the spinbox.

See the "broken" (using current dev branch) and "working" (current dev branch with the commit reverted) screenshots that are attached below. I also added a trivial reproducer which adds some margin and padding using a stylesheet, this seems to happen with all QSpinBoxes that have stylesheets applied.

For reference, we observe this in OBS Studio when using updated Qt (e.g. obsproject/obs-studio#11649).