Change icon of built in VPN

[bilguunc]

Current icon of built in VPN is little bit confusing for me at least. x figure left VPN text is confused to close button of Firefox or tabs. 

Idea:

- Just VPN with grey background/text color  when not connected / idle 

- Just VPN with green background/text color when connected successfully

- Just VPN with yellow background/text color when connecting to VPN

- Just VPN with red background/text color when connection to VPN failed 

[Jon]

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[Magzar]

Good idea though I would prefer if it could depend on the theme too as green might look ugly for some

The x button could be changed to an empty one with just an outline when not used, and a filled in one when it is active along with the outline.