ai/live: Add delayed teardowns to trickle server

[j0sh]

Draft for now as I'm doing a final round of e2e testing locally.

Commits

ai/live: Add delayed teardowns to trickle server.

This allows for reads to a channel after closing, but not writes.

Closed channels are swept after the idle timeout period.

ai/live: Add unit tests for trickle delayed teardowns.
Add a mock for the time.Now function for testing.

ai/live: Const-ify status code 470 to StatusNoSegment

[codecov]

Codecov Report

Attention: Patch coverage is 70.73171% with 12 lines in your changes missing coverage. Please review.

Project coverage is 31.80072%. Comparing base (dc64e3d) to head (3ec80f6).

Files with missing lines	Patch %	Lines
trickle/local_publisher.go	0.00000%	9 Missing ⚠️
trickle/trickle_server.go	93.33333%	2 Missing ⚠️
trickle/trickle_subscriber.go	50.00000%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #3681         +/-   ##
===================================================
+ Coverage   31.74935%   31.80072%   +0.05137%     
===================================================
  Files            156         156                 
  Lines          47349       47370         +21     
===================================================
+ Hits           15033       15064         +31     
+ Misses         31434       31421         -13     
- Partials         882         885          +3     

Files with missing lines	Coverage Δ
trickle/trickle_subscriber.go	71.95122% <50.00000%> (ø)
trickle/trickle_server.go	74.19355% <93.33333%> (+3.92328%)	⬆️
trickle/local_publisher.go	18.36735% <0.00000%> (-2.56288%)	⬇️

... and 1 file with indirect coverage changes

---

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Files with missing lines	Coverage Δ
trickle/trickle_subscriber.go	71.95122% <50.00000%> (ø)
trickle/trickle_server.go	74.19355% <93.33333%> (+3.92328%)	⬆️
trickle/local_publisher.go	18.36735% <0.00000%> (-2.56288%)	⬇️

... and 1 file with indirect coverage changes

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[leszko]

Looks good. I'll do the review again and approve when the PR is set to Ready. But in general, all looks good.

[mjh1]

Likewise, looks good