TCPStream/UDPSocket tos/set_tos methods

[dvolodin7]

Is your feature request related to a problem? Please describe.
Some network applications rely on proper marking of egress packets using ToS/DSCP fields. Routing protocols,
management traffic, VoIP applications and so on.

ToS can be set on socket level using setsockopt call, using IPPROTO_IP level and IP_TOS option.
TCPStream and UDPSocket already have functions:

• ttl
• set_ttl

for getting an setting TTL field. TTL is manipulated via the same setsockopt/getsockopt calls.

Describe the solution you'd like
Adding methods

• tos
• set_tos

for getting socket's ToS settings will be good addition for a large spectre of network applications.

Describe alternatives you've considered
Direct usage of setsockopt on raw socket handle still possible, and can be used as workaround.

Additional context
N/A