* Add trace/embedded
* Update trace impl to use trace/embedded
* Add noop pkg to replace no-op impl in trace pkg
* Use trace/embedded in global impl
* Use trace/embedded in SDK impl
* Update opencensus bridge
* Update opentracing bridge
* Add changes to changelog
* Update trace/doc.go
Co-authored-by: David Ashpole <dashpole@google.com>
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Co-authored-by: David Ashpole <dashpole@google.com>