Detector of VFS high level events related to client side state

[dkulieshov]

Overview

The idea is to provide a detector or detectors to be able to transfer all client side related events that happens on VFS through some event transport from server to client.

Description

We need to be able to track events that impact client side and happens on server side on virtual file system so we could properly correspond. The most obvious example of such detector usage is tracking of file content changes. The workflow is the following:

• A user opens a file in IDE editor (a new editor tab with file's content)
• Client-side sevice tracks sees state changes and reports to the server-side that a file is opened
• Now server-side detector is aware of that and starts tracking of that file's state on VFS
• It watches and knows when changes (irrespective of source) are made
• It informs (via event transport) client-side that file's content is changed
• Client updates file's content in an editor's tab

[TylerJewell]

@dkuleshov - can you cross-link the PR for this please?

[dkulieshov]

This issue was resolved under #2339