[quicwg/base-drafts] Pseudo code issue (#1724)

[Lars Eggert <[e-mail]>]

i think there is an issue in the pseudo code (but I may be wrong - I find the code much more difficult to follow than an actual textual explanation.)

In `OnAckReceived`, there is the following call sequence:
```
       DetectLostPackets(ack.largest_acked_packet)
       SetLossDetectionTimer()
```

`DetectLostPackets` calls `OnPacketsLost`, which reduces `in_flight` potentially to zero. Then in `SetLossDetectionTimer`, the timer is cancelled via `loss_detection_timer.cancel()`.

This causes no retransmissions to happen, at least when (blindly) implementing the pseudo code.

Related to that, it is not clear where exactly the pseudo code expects actual retransmissions to happen. There is code in `OnLossDetectionTimeout` (`RetransmitAllUnackedHandshakeData`, `SendOnePacket`, `SendTwoPackets`) but what those do is not explained. There is also a comment in `DetectLostPackets` ("Inform the congestion controller...") but it remains unclear when and how that would lead to retransmissions.

IMO, if we rely on pseudo code for this document, it needs a lot more work to make sure it actually does what is intended. (My preference would be to instead describe the concepts in text.)

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