Not sure why we used 256 given the typical shaders used with Qt.
A prealloc of 256 means 8328 bytes on the stack, which feels excessive,
and shows up in profiler hotspots for some reason.
Task-number: QTBUG-125087
Pick-to: 6.7 6.6 6.5
Change-Id: Ibae26dae95cbc8d0e9ea53423daa151e768a93b2
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
(cherry picked from commit fb2e33b65aea28609996c4e1ac59c3ee75e5b839)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
a682cb9596