Currently, we allocate memory for elements one by one which can get
pretty slow when adding many elements.
[ChangeLog][QtCore][QVarLengthArray] Reduced number of memory
allocations in emplace() by allocating more memory at once.
Fixes: QTBUG-97489
Pick-to: 6.2
Change-Id: Idfb5b5946b047d5215c8ed00770574249f9f5d40
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>