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