Emit the error code and type to the tracing span for inbound calls

[deepanshumehndiratta]

Changelog

1. Emit the error code and type to the tracing span for inbound calls

Description

This change adds the error type and code (for system errors) to the tracing spans for inbound requests.

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[codecov]

Codecov Report

Patch coverage: 71.79% and project coverage change: +0.10% 🎉

Comparison is base (0c11cc2) 88.78% compared to head (f3409ca) 88.89%.
Report is 5 commits behind head on dev.

❗ Current head f3409ca differs from pull request most recent head 51344aa. Consider uploading reports for the commit 51344aa to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #903      +/-   ##
==========================================
+ Coverage   88.78%   88.89%   +0.10%     
==========================================
  Files          43       43              
  Lines        4440     4510      +70     
==========================================
+ Hits         3942     4009      +67     
  Misses        379      379              
- Partials      119      122       +3     

Files Changed	Coverage Δ
outbound.go	87.86% <33.33%> (+0.72%)	⬆️
messages.go	91.58% <50.00%> (-6.27%)	⬇️
inbound.go	79.51% <61.53%> (-2.88%)	⬇️
mex.go	75.42% <76.00%> (+2.91%)	⬆️
connection.go	88.39% <88.88%> (+3.40%)	⬆️
relay.go	85.77% <100.00%> (+0.06%)	⬆️
relay_messages.go	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[vprithvi]

I feel something like this could be easier to read:
(Also - we can add the error message to the span log)

	if span := response.span; span != nil {
		if response.systemError {
			ext.Error.Set(span, true)
			span.SetTag("rpc.tchannel.error_type", "system")
			span.SetTag("rpc.tchannel.system.error_code", GetSystemErrorCode(response.err))
			span.LogKV("rpc.tchannel.system.error_message", GetSystemErrorMessage(response.err))
		} else if response.applicationError {
			ext.Error.Set(span, true)
			span.SetTag("rpc.tchannel.error_type", "application")
		}

[cinchurge]

sorry for coming late to this. why weren't these changes tested?