Add public label to any channel using public PSK

[willhubs]

Whenever a channel is displayed, if it's using the public PSK of AQ== there would be a designation of public next to the channel name.

So in the "contacts" tab and when sending messages it would say LongFast(public) instead of just LongFast.

This would help clarify for new users that what they are sending is on a public channel.

[mverch67]

This information is actually already presented by the lock symbol:

• green closed lock: secure channel
• yellow key symbol: public channel with known key
• red open lock: empty encryption key

[willhubs]

Which seems to cause a lot of confusion to people, but I understand if that's what works best for the space.

Also might not be used the same way across all interfaces.

https://www.reddit.com/r/meshtastic/comments/1lg5dl1/primary_channel_icon/
https://www.reddit.com/r/meshtastic/comments/1lfssjq/new_guy_here/
https://www.reddit.com/r/meshtastic/comments/1lflfzl/primary_chanel_psk_problems/