LayoutGroup: handleManualLayout() should set contentMinWidth and contentMinHeight on the LayoutBoundsResult

[joshtynjala]

this._layoutResult.contentMinWidth = maxX;
this._layoutResult.contentMinHeight = maxY;

Should also check if handleLayoutResult() should use contentMinWidth and contentMinHeight, like the override in LayoutViewPort.

Measurement tests for ScrollContainer and Panel will need adjusting.