Do not forget to merge metric/global into top level package

[bogdandrutu]

See https://github.com/open-telemetry/opentelemetry-go/blob/main/metric/global/global.go, this needs to be consistent with trace and be available under go.opentelemetry.io/otel.

[Aneurysm9]

That cannot happen until after the metrics API is in a v1.x module.

[bogdandrutu]

That cannot happen until after the metrics API is in a v1.x module.

I know my english is very bad, but I tried to point in the title that this should be a "tracking" issue to "not forget" to do this. It does not say do it now.

[MrAlias]

Resolved by #3818