feat(proto): expand qlog support

[Frando]

This expands the qlog support:

• Allow to set the vantage point for qlog traces
• Record frames for received packets
• Record frames for sent packets
• Record ConnectionStarted event

[flub]

Generally looks great, but let's add good doc comments. Even for internal APIs.

The other main comment is that the qlog module is cfg-disabling all the bodies of functions so that the callsites don't have to have cfg everywhere. I think you should continue that style for the newly added methods. That would get rid of a lot of cfg lines.

[flub]

I think the philosophy of this module is to keep all/most the cfgs inside the function bodies. That way the call sites are not littered with cfgs. And the compiler is expected to optimise out the noop function calls. So you probably should follow the same pattern for these new impls?

[Frando]

Yes, maybe. For QlogRecvPacket it's straightforward, will change. I kept the cfg initially for QlogSentPacket::frame, which takes a qlog::QuicFrame. Constructing this from the raw data sometimes involves calculations, so to make sure to not do these when qlog is disabled I made the fn be configured out in that case. Maybe I just keep the cfg for that one only.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 84.30584% with 78 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.68%. Comparing base (cb60f6d) to head (145ba10).

Files with missing lines	Patch %	Lines
quinn-proto/src/connection/qlog.rs	83.39%	46 Missing ⚠️
quinn-proto/src/config/transport.rs	0.00%	16 Missing ⚠️
quinn-proto/src/connection/mod.rs	89.18%	16 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##           main-iroh     #181      +/-   ##
=============================================
+ Coverage      76.38%   76.68%   +0.30%     
=============================================
  Files             83       83              
  Lines          22286    22663     +377     
=============================================
+ Hits           17023    17379     +356     
- Misses          5263     5284      +21     

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