Add proxy support for initial `ivpn login`

[chibitanaka]

Add proxy support for initial login

Description

I have a valid account, but due to ivpn bans in my country it seems I can't reach auth servers. To make matters worse proxychains ivpn login ignores my proxy config as I presume it happens on daemon level. Without this feature I'm effectively locked out of service :(

Describe the solution you'd like

To be able to specify HTTP/SOCKS5 proxy for initial login