* New label set API
* Checkpoint
* Remove label.Labels interface
* Fix trace
* Remove label storage
* Restore metric_test.go
* Tidy tests
* More comments
* More comments
* Same changes as 654
* Checkpoint
* Fix batch labels
* Avoid Resource.Attributes() where possible
* Update comments and restore order in resource.go
* From feedback
* From feedback
* Move iterator_test & feedback
* Strenghten the label.Set test
* Feedback on typos
* Fix the set test per @krnowak
* Nit
* Remove LabelSet frmo api/metric
* SDK tests pass
* Restore benchmarks
* All tests pass
* Remove all mentions of LabelSet
* Test RecordBatch
* Batch test
* Improves benchmark (some)
* Move the benchmark to match HEAD
* Align labels for GOARCH=386
* Add alignment test
* Disable the stress test fo GOARCH=386
* Fix bug
* Move atomic fields into their own file
* Add a TODO
* Comments
* Remove metric.Labels(...)
* FTB
Co-authored-by: Liz Fong-Jones <lizf@honeycomb.io>