Quick pick: allow to handle middle mouse button specifically

There is a desire in https://github.com/microsoft/vscode/issues/147562 to handle middle mouse button different for recently opened picker, same as when you press modifier key to force open into new window. The picker API has `onKeyMods` which is a way for the client of the API to get hold of the modifier keys that were pressed when selecting an item, maybe something similar would be possible for mouse buttons as well: https://github.com/microsoft/vscode/blob/35ab68698ae4cdb37ed9eeef2e16d78d0aab88c0/src/vs/workbench/browser/actions/windowActions.ts#L146 Interestingly in the quick access API I am dealing with this already, but that is only possible because I have low level access to the quick pick widget and I am not using the `pick` API: https://github.com/microsoft/vscode/blob/35ab68698ae4cdb37ed9eeef2e16d78d0aab88c0/src/vs/base/parts/quickinput/browser/quickInput.ts#L872