Censorship circumvention: share IP configurations between TDLib instances

[vkryl]

For now TDLib instances do not help each other while finding their way to Telegram servers.

Sharing some configuration between instances could improve some cases:

• When user has multiple accounts, one account works properly, other does not. If they are located in the same DC, sharing information between instances would help user getting the second account online.
• When adding new account, new TDLib instance gets created. If existing TDLib instances would share some configuration information with it, it could reduce time needed for the initial connection.
• If multiple accounts are located in the same DC, there's (most likely) no need in doing all censorship circumvention methods on both instances. If only one instance would do it, CPU / data usage needed by censorship circumvention methods could be reduced.

[levlam]

Censorship circumvention is much harder then just finding a working IP through different sources. There is a lot of important implementation details, dependent on exact user account, which can't be easily shared between different accounts. Despite it seems to be right thing to share working IPs between different accounts running on the same device, there is really a lot of things that could go wrong if that happens.