BYOC: add orch swap reporting same as lv2v

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What does this pull request do? Explain your changes. (required)

Removes generic error reporting in favor of more specific stream_trace event similar to how lv2v pipeline reports orchestrator swaps.

lv2v orchestrator swap event reporting

go-livepeer/server/ai_mediaserver.go

Lines 742 to 753 in ab55f82

	monitor.SendQueueEventAsync("stream_trace", map[string]interface{}{
	"type": "orchestrator_swap",
	"stream_id": params.liveParams.streamID,
	"request_id": params.liveParams.requestID,
	"pipeline": params.liveParams.pipeline,
	"pipeline_id": params.liveParams.pipelineID,
	"message": err.Error(),
	"orchestrator_info": map[string]interface{}{
	"address": params.liveParams.sess.Address(),
	"url": params.liveParams.sess.Transcoder(),
	},
	})

Specific updates (required)

• remove sendErrorEvent generic error reporting
• replace with stream trace event orchestrator_swap type

How did you test each of these updates (required)

Does this pull request close any open issues?

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 32.22090%. Comparing base (a38b81a) to head (4621911).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #3865         +/-   ##
===================================================
+ Coverage   32.15928%   32.22090%   +0.06162%     
===================================================
  Files            170         170                 
  Lines          41310       41321         +11     
===================================================
+ Hits           13285       13314         +29     
+ Misses         27023       27005         -18     
  Partials        1002        1002                 

Files with missing lines	Coverage Δ
byoc/stream_gateway.go	58.30986% <100.00000%> (+0.65607%)	⬆️

... and 5 files with indirect coverage changes

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Files with missing lines	Coverage Δ
byoc/stream_gateway.go	58.30986% <100.00000%> (+0.65607%)	⬆️

... and 5 files with indirect coverage changes

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