Prerelease changes

• Charting: Adding custom Callout support for HorizontalBarChart, StackedBarChart and DonutChart. (PR #15697 by khmakoto)
• Charting: Fixing uncaught type error in VerticalStackedBarChart and made minor edits to margins. (PR #15699 by khmakoto)
• Charting: Adding support for bar gaps and rounded corners in VerticalStackedBarChart. (PR #15704 by khmakoto)
• Charting: Added line feature to VerticalBarChart. (PR #15705 by khmakoto)