avoid processing-intensive painting of high number of tiny dashes

avoid processing-intensive painting of high number of tiny dashes

Origin: upstream, commits:
 https://code.qt.io/cgit/qt/qtbase.git/commit/?id=f4d791b330d02777
 https://code.qt.io/cgit/qt/qtbase.git/commit/?id=6b400e3147dcfd8c
 https://code.qt.io/cgit/qt/qtbase.git/commit/?id=84aba80944a2e1c3
 https://code.qt.io/cgit/qt/qtbase.git/commit/?id=81a7344e1dea5622
Last-Update: 2021-11-27

When stroking a dashed path, an unnecessary amount of processing would
be spent if there is a huge number of dashes visible, e.g. because of
scaling. Since the dashes are too small to be individually visible
anyway, just replace with a semi-transparent solid line for such
cases.

Gbp-Pq: Name CVE-2021-38593.diff