udp_rtt in more tests

[dtaht]

Since ping is being spoofed by starlink, a udp ping test in combination with tcp_nup/tcp_ndown or appears needed.

also I am loving sampling things at a 3ms interval in irtt general.

I think a new generation of tests is needed. rrulv2 ?

I am thinking nup and ndown would be good names for something that leveraged irtt, but I am not sure how using a much smaller interval than socket-stats for irtt could work.

[dtaht]

and/or call it udp-owd so as to plot both directions