VSCE: log user events using LogUserEvent endpoint

Created by: abeatrix

Ref to Slack thread C01LZKLRF0C

logUserEvent is the only place where “last active” and “last active in code host or code view” values are set, which are shown in side-admin/usage-stats.

Even though the LogUserEvent endpoint has been deprecated, it's the only endpoint that logs user activities. As a result, we should also log user events using the deprecated endpoint for backward compatibility