[#3112] Add supprt for TCP_INFO when using EpollSocketChannel

Motivation:

On linux you can gather various metrics using getsockopt(..., TCP_INFO...). We should support this in EpollSocketChannel.

Modifications:

Add EpollSocketChannel.tcpInfo() which return TcpInfo that holds all relevant metrics.

Result:

TCP_INFO is supported now.
Because all the fields of TCP_INFO are unsigned, we should use wider types - int for u8, int for u16, long for u32.