Implement project load event in preview version of the extension

[dibarbet]

O# reports when a project is loaded or changed,

vscode-csharp/src/observers/TelemetryObserver.ts

Line 102 in eb0d88d

private handleProjectConfigurationReceived(event: ProjectConfiguration, telemetryProps: { [key: string]: string }) {

We need to add similar functionality for the preview extension, but we'll likely be limiting it to the initial initialization, instead of all project changes.

[arunchndr]

@dibarbet Would you confirm the latest on this is that the load event went in, but changed is not. If so, is the event name the same?

cc: @webreidi