Add span format tag for jaeger-collector

[guo0693]

Signed-off-by: jung jung@uber.com

Which problem is this PR solving?

• Resolves Add span format tag for each span #1490

Short description of the changes

• include span format tag for every processed span in the collector

[guo0693]

Screenshot of running hotRod locally with the changes.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@7a1f334). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #1493   +/-   ##
=========================================
  Coverage          ?   99.81%           
=========================================
  Files             ?      181           
  Lines             ?     8652           
  Branches          ?        0           
=========================================
  Hits              ?     8636           
  Misses            ?        8           
  Partials          ?        8

Impacted Files	Coverage Δ
model/converter/thrift/jaeger/to_domain.go	100% <100%> (ø)
cmd/collector/app/span_processor.go	100% <100%> (ø)

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