fix: v3bwfile: network means by relay type

Calculate network stream and filtered bandwidth averages per relay
type, to obtain bandwidth weights the same way as Torflow.

Closes #40059.
7 jobs for maint-1.1_issue40059_relay_type in 47 minutes and 15 seconds (queued for 23 seconds)
latest
Status Name Job ID Coverage
  Test
passed python36tor035 #15315

00:11:18

passed python36tor041 #15316

00:11:28

passed python36tor042 #15317

00:11:18

passed python36torstable #15318

00:11:31

passed python37 #15319

00:13:58

passed python38 #15320

00:11:20

passed python39 #15321

00:11:19