feat(trace-exporter)!: send span kind to cloud trace

[aabmass]

BREAKING CHANGE: add span kind is now sent with traces.

[codecov]

Codecov Report

Merging #293 (e9f00ab) into master (c7c0d95) will increase coverage by 0.22%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #293      +/-   ##
==========================================
+ Coverage   95.86%   96.08%   +0.22%     
==========================================
  Files          12       12              
  Lines         387      409      +22     
  Branches       71       78       +7     
==========================================
+ Hits          371      393      +22     
  Misses         16       16              

Impacted Files	Coverage Δ
...pentelemetry-cloud-trace-exporter/src/transform.ts	98.05% <100.00%> (+0.33%)	⬆️
...es/opentelemetry-cloud-trace-exporter/src/types.ts	100.00% <100.00%> (ø)

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[punya]

Small nits, but looks good overall.

[weyert]

This PR sounds interesting @aabmass Does this in any change the way the span is represented in Google Trace UI?

[aabmass]

I don't think the UI shows span kind at the moment, but it is definitely saved in the backend