chan: Move interface to get socket TCP info

Originally, the tcp_info data needed for KIST was done in the scheduler_kist.c file because it is KIST specific.

This commit moves this code into the channel subsystem and puts the storage of that data into the channel itself instead of a socket table.

This allows any subsystem to access this information and this removes the need for the socket table entry which was uneeded overhead especially allocating very small chunks of memory at every scheduling loop.

No behavior change.

Related to #40731 (closed)

Signed-off-by: David Goulet dgoulet@torproject.org