Add TX/RX message direction to socketcan

[tysonite]

References #773 and #776

[tysonite]

Don't judge me too much, please. :) My first try to submit something there. I actually got a pointer to implement that looking into candump tool and SocketCAN doc 4.1.7 section.

Also, I am not sure if this change also needs to take into account ancdata returned by recvmsg (https://docs.python.org/3/library/socket.html#socket.socket.recvmsg).

[codecov]

Codecov Report

Merging #780 into develop will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           develop    #780      +/-   ##
==========================================
+ Coverage    69.48%   69.5%   +0.02%     
==========================================
  Files           70      70              
  Lines         6557    6556       -1     
==========================================
+ Hits          4556    4557       +1     
+ Misses        2001    1999       -2

[hardbyte]

Thanks for the contribution @tysonite