A sliver that places multiple box children in a linear array along the main axis.

Each child is forced to have the SliverConstraints.crossAxisExtent in the cross axis but determines its own main axis extent.

SliverList determines its scroll offset by “dead reckoning“ because children outside the visible part of the sliver are not materialized, which means SliverList cannot learn their main axis extent.Instead,newly materialized children are placed adjacent to existing children.