Multiple fixes and enhancements to ICE-TCP

[paullouisageneau]

This PR fixes/enhances multiple things related to the ICE-TCP implementation:

• Implement ICE-TCP read and write with buffering, otherwise receiving a partial datagram from remote makes the poll loop spin, and sending when TCP socket buffer is full may write a partial datagram which breaks framing.
• Fix out-of-bounds access to pfds array on agent destruction
• Add two TCP active candidates for IPv6 and IPv4 to properly advertise IPv6 support
• Populate socktype everywhere and compare socktypes to prevent confusion between UDP and TCP address
• Refactor TCP connected callback and introduce state to handle connecting state

@Sean-Der Could you please test if things look good on your side with the changes?

[Dw9]

lol,I should have checked the community submissions first. @paullouisageneau I’ve also recently implemented ice-tcp related features to support WebRTC over TCP.