WorksheetInDashboard parameter for the displayDialogAsync function

[florent-guinard]

In the JavaScript API there's a worksheetInDashboard parameter for the showExportDataDialog function that allows us to specify which Worksheet we want to download data from when the current embedded Viz is a Dashboard.

We'd like a similar feature in the Embedding API: the displayDialogAsync function only takes an "export type" parameter and we're currently unable to display the dialog to download data of Worksheets other than the first one of an embedded Dashboard.

The Workbook.activateSheetAsync function changes the sheet displayed to a specific Worksheet instead of the Dashboard, something we'd like to avoid (changing the sheet displayed removes any filter applied/mark selected).