[EuiDataGrid] Expose prop to control number of prefetched rows for virtualized scrolling

[flash1293]

Right now it's not possible to control how many rows of the virtualized table body get preloaded and the current settings are pretty conservative in pre-rendering rows.

As it depends on the certain context whether more pre-rendering makes sense, we should allow the consumer to control this setting by setting a prop on the data grid.

[chandlerprall]

This new prop should probably accept all the options for VariableSizeGrid and pass them through.