* Update metric Kind to InstrumentKind
* Update all the other modules with Kind rename
* Update metric Descriptor with instrument Kind rename
* Update other modules with Descriptor method rename
* Update OTLP exporter test field name
* Rename kind filenames
* Add changes to CHANGELOG
* Fix documentation for Grouping and PrecomputedSum
* Rename meter.go to metric.go
* Move descriptor.go into metric.go
* Move must.go into metric.go
* Move instruments into metric_instrument.go
* Rename metric api_test.go to metric_test.go
* Move instrumentkind_test.go into metric_test.go
* Rename sdkapi.go metric_sdkapi.go
* Move api/metric into otel
* Update to use moved packages
* Rename otel.go to error_handler.go
* Add changes to CHANGELOG
* Fix merge conflict resolution error
