fix misplacement of placeholder text in QLineEdit with RTL content

fix misplacement of placeholder text in QLineEdit with RTL content

Origin: upstream, https://code.qt.io/cgit/qt/qtbase.git/commit/?id=dc794f7622bc00f7
Last-Update: 2021-06-16

The placeholder text was rendered in the wrong position after clicking
on the clear button in a QLineEdit with right-to-left content. The
button was still taking up space while it was fading out, so the first
paintEvent rendered the placeholder with space reserved for the clear
button. Once the button gets hidden, no new update was issued, so
garbage was left behind.

Fix this by not giving a fading-out clear button any margin space. The
result of this is that the placeholder text is visible underneath the
fading-out clear button. This is preferable to the placeholder text
being first rendered next to the fading-out clear button, and then
popping to the edge when the clear button is hidden (which would have
been the result of issuing a complete update for the line edit at the
end of the fade-out animation).

Gbp-Pq: Name fix-misplacement-of-placeholder-text-in-QLineEdit.diff