Add methods to operate and get component rendered on DetailsRow in GridTester

[TatuLund]

There is a method to get cell component like below.

$(Button.class, test(grid).getCellComponent(0, 5)).first().click();

But there is no method to get details row content,

E.g. it could be like:

var detailsComponent = test(grid).getDetailsComponent(0)).first();

The above would return component rendered for details row linked to first row if it is open. If it is closed it would throw e.g. IllegalStateException.

Also it would be useful to have:

var detailsOpen = test(grid).isDetailsOpen(0);

The above would return true if the details row is open.

Doing click on Grid cell should open details as a side effect if grid.setDetailsVisibleOnClick(true) is used.