feat(conn): expose socket option and read buffer size options

[anpep]

Similar in spirit to #5, except it also exposes the SetOption() method for the ability to set the netlink.NoENOBUFS option on the netlink socket, in which case the socket won't be closed when no buffer space is available. In this case, missed uevents can be detected by observing a gap in the sequence numbers (SEQNUM) of uevents.

[flotter]

Hi @mdlayher or @SuperQ! Could you let us know if it will be possible to get these features merged ? We are trying to make our uevent handler a little more robust against dropped packets.