Metered connection: opening local files uses data

[kycutler]

Testing #297205

1. Use a tool like TCPView to measure network usage. Filter to Code - Insiders.
2. Open a workspace and make sure metered connection is on.
3. Repeatedly swap the open editor (i.e. open file A, open file B, open file A, open file B, ...)
4. Notice that around 5-10KB of data gets sent each time a file is opened.

Unfortunately I don't have any info on what the data is, but it seems to be sent regardless of the metered setting, even with extensions disabled.

[dmitrivMS]

I suspect it may be NES...