Implement Brave VPN on Windows

[bsclifton]

Description

Part of parent issue #15804

The goal here would be to create an implementation in brave-core which handles VPN on Windows (7, 8, 10). Each OS can provide an OS specific implementation for a "VPN Service".

This would need the ability to:

• Create a VPN connection with the OS.
• Update a connection (if details change)
• Connect to the VPN
• Disconnect from the VPN
• Remove the VPN connection from the OS

I've created a proof of concept here which has example Win32 code for viewing and creating entries:
https://github.com/bsclifton/winvpntool/blob/master/main.cpp

We'll want to take this proof of concept and polish it up and add the missing functionality (remove, etc) and put it into the Windows specific implementation for VPN Service in brave-core.

What the user would see in Windows

VPN connections are visible in Windows 10 from:
Settings > Networking & Internet > VPN

[simonhong]

@bsclifton Changed to QA/No because this issue will not cover the UI. So, can't test easily with browser.
When we have UI for premium, I think we could test. WDYT?

[bsclifton]

@simonhong SGTM! 😄