Fixes #1677

Changes

• modify the definition of code.function.name to include fully qualified name
• deprecate code.namespace as the information is included in code.function.name.

This is a breaking change for which any producer/consumer of code.function.name, code.function (deprecated) or code.namespace is impacted. The changes are however expected to be performed once all attributes in code.* namespace have been made stable.

Because the change is not a simple rename, we can't use the schema transformation, even if we had a way to perform complex transformations made possible by open-telemetry/opentelemetry-specification#4427, the transformation would have to be platform-specific and we might not have the ability to do that by relying only on the available data.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• schema-next.yaml updated with changes to existing conventions.