* Update RegisterCallback and Callback decls
RegisterCallback accept variadic Asynchronous instruments instead of a
slice.
Callback accept an observation result recorder to ensure instruments
that are observed by a callback.
* Update global impl
* Update noop impl
* Update SDK impl
* Fix prometheus example
* Fix metric API example_test
* Remove unused registerabler
* Rename ObservationRecorder to MultiObserver
* Update Callback documentation about MultiObserver
* Remove the Observe method from async inst
* Revert to iface for Observers
* Fix async inst docs
* Update global async delegate race test
* Restore removed observe doc
* Remove TODO
* Remove stale comment
* Update changelog
* Empty All of the metrics dir
* Add instrument api with documentation
* Add a NoOp implementation.
* Updated to the new config standard
* Address PR comments
* This change moves components to sdk/metrics
The Moved components are:
- metric/metrictest
- metric/number
- metric/internal/registry
- metric/sdkapi
* The SDK changes necessary to satasify the new api
* This fixes the remaing tests.
* Update changelog
* refactor the Noop meter and instruments into one package.
* Renamed pkg.Instruments to pkg.InstrumentProvider
Co-authored-by: Aaron Clawson <MadVikingGod@users.noreply.github.com>