Test cancelable input/quick pick

[jrieken]

• any os @bpasero

tests #9377

The calls for showInputBox and showQuickPick now allow to pass in a cancellation token that hides them again. Test that cancelling programmatically yields the same results as manually (promise resolves to undefined).

[jrieken]

FYI - to test against the latest API do the following:

• open your extensions package.json file
• change the engine.vscode property to *
• run npm run postinstall (assuming you have the vscode module as dev-dependency)
• undo the engine-version change from step 2