Optimise QgsCoordinateTransform::transformBoundingBox (qgis#59300)

Using std::vector is preferable here, as we don't need implicit
sharing of the container or want the extra overhead associated
with it

Author: nyalldawson

src/core/proj/qgscoordinatetransform.cpp

@@ -632,11 +632,9 @@ QgsRectangle QgsCoordinateTransform::transformBoundingBox( const QgsRectangle &r
   QgsRectangle bb_rect;
   bb_rect.setNull();
 
-  // We're interfacing with C-style vectors in the
-  // end, so let's do C-style vectors here too.
-  QVector<double> x( nXPoints * nYPoints );
-  QVector<double> y( nXPoints * nYPoints );
-  QVector<double> z( nXPoints * nYPoints );
+  std::vector<double> x( nXPoints * static_cast< std::size_t >( nYPoints ) );
+  std::vector<double> y( nXPoints * static_cast< std::size_t >( nYPoints ) );
+  std::vector<double> z( nXPoints * static_cast< std::size_t >( nYPoints ) );
 
   QgsDebugMsgLevel( QStringLiteral( "Entering transformBoundingBox..." ), 4 );