Parameter hints should not use aria.alert

Instead they should use activeDescendent same as suggest widget. Code pointer where parameterHints are currently using aria alert https://github.com/microsoft/vscode/blob/8451f8bd913914aac17b6b3273b6ed0db137a217/src/vs/editor/contrib/parameterHints/parameterHintsWidget.ts#L251

As @pawelurbanski points out: Using activeDescendant for parameter hints.

• Currently, the hints are outputted by the alert function, which has 2 nasty attributes:
• If you do not modify the message with a counter, repeate messages are filtered out,
• If you modify the message you go crazy after hearing: string appeared 29 times,
• When there is more than 1 paremter all the items are read as a single string with no pauses,
• The alert is an offscreen DOM element that is not-focusable so you can’t scroll through the items.
• I just disable the hints all together and use Ctrl+Shift+Space every now and then…

fyi @alexdima