As a user, I configure the overall requirement coverage chart to show a flat list of requirements

The user must be able to configure the Requirement Coverage charts to display a flat list of Requirement issues (Requirements and Sub-Requirements). The parent Requirement should also be included in the chart because it might contain Tests directly associated with it.

This option must be available in the chart screen and it's default value must be setted in the Xray Requirement Coverage configuration page.

When this option is enabled, the drill-down details table should also contain a flat list of Requirements.

This option should also be included in the gadgets: Overall and Historical.