Create unit test for dirserv_read_measured_bandwidths
So that we ensure that tor will still continue to read V3BandwidthsFile documents when we add new headers to it in version 1.1.0, as proposed in #25869 (moved)
So that we ensure that tor will still continue to read V3BandwidthsFile documents when we add new headers to it in version 1.1.0, as proposed in #25869 (moved)