Improve notification APIs

[mattacosta]

Summary
The current notification API does not currently provide a distinction between notifications (these don't require user interaction) and prompts (these do require user interaction) or implement the required functionality for additional notification features that have been requested. This also results in instances where the wrong UI element is used, which hinders the workflow of some users.

Proposal

Add a notification manager containing related notification methods to the window object.
Ex: window.notifications.addError('Something bad happened.');

The manager would provide the following methods and events:

• addInfo(): accepts a message and options parameters, returns a notification object
• addWarning(): accepts a message and options parameters, returns a notification object
• addError(): accepts a message and options parameters, returns a notification object
• getNotifications(): returns a list of notifications
• onDidAddNotification: event that invokes a callback that receives a notification object
• removeNotification(): accepts a notification, tag, or extension id

 
The NotificationOptions object would also contain the following properties:

• title: string
• details/source: markup?
• buttons: array
• tag/group: string
• isExpanded: boolean (for backward-compatibility)

 
The Notification object contains information about the added notification and an onDismiss event. This object would also be required for other features, such as #44122.

Add a generic showDialog method to the window object.

// TODO: This method would... accept simple message parameters, or an object that implements an abstract Dialog class? Could these dialogs also show custom markup?

Backwards compatibility
The current APIs should be marked deprecated.

If desired, an "adapter" class or service could also redirect deprecated API calls to the most appropriate (notification or dialog box) action, thereby allowing use of updated UI elements by deprecated code in most cases.

[jrieken]

Well, there is a little known flag to make messages modal, so enforce user to act on them.

[vscodebot]

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Thanks for your understanding and happy coding!

[ORESoftware]

I have a question - is there documentation on how to ping VSCode from another process on the same machine and tell VSCode to display a notification? Is VSCode listening on localhost?