Test run hang in PipeReader.ReadAsync

[AArnott]

This pipeline hung after running tests, waiting on this "stack" of async tasks:

0000020b0e067ce0 00007ffa567dd9d8      152          0 Nerdbank.Streams.MultiplexingStream+V2Formatter+<DisposeAsync>d__5
0000020b0e067d78 00007ffa567ddd68      152          1 Nerdbank.Streams.MultiplexingStream+<DisposeAsync>d__55
0000020b0e067e10 00007ffa56866620      128          0 MultiplexingStreamTests+<DisposeAsync>d__9

The formatter was waiting on the read semaphore:
https://github.com/AArnott/Nerdbank.Streams/blob/db117800aedfae7ae2624e89203179c7a29dcaf3/src/Nerdbank.Streams/MultiplexingStream.Formatters.cs#L292

Dump file

[AArnott]

The sequence file indicates that MultiplexingStreamV3Tests.CommunicateOverOneChannel never completed.