This commit cotributes to replicating the behaviour of Edge:evaluate as
it is in WebKit - it must not wait for the execution of script to obtain
the result, in case evaluate is called inside a WebView callback. This
commit also makes sure that OpenWindowListeners are execute
synchronously or asynchronously depending on if the
handleNewWindowRequested is called from the evaluate script. Moreover,
this enables all the tests which were failing because of Edge:evaluate
limitations.

contributes to
https://github.com/eclipse-platform/eclipse.platform.swt/issues/1771 and https://github.com/eclipse-platform/eclipse.platform.swt/issues/1919