Add "s3/"-prefix to S3 destination.service.resource

[JonasKunz]

Description

Implementation issue for spec change elastic/apm#738. The spec for the context.destination.service.resource span field for AWS S3 has been changed from ${bucketName} to s3/{bucketName}.

This change should be classified as a bugfix in the agent release notes and the release notes should state that this change is potentially breaking:

• It can break the history of the S3-Spans / metrics for users relying on context.destination.service.resource
• If users happen to run agents both with and without this fix (for same or different languages), the same S3-buckets can appear twice in the service map (with and without s3-prefix)

Agent Issues

• [ ] https://github.com/elastic/apm-agent-java/issues/2946
• [ ] https://github.com/elastic/apm-agent-nodejs/issues/3084
• [ ] https://github.com/elastic/apm-agent-python/issues/1717
• [ ] https://github.com/elastic/apm-agent-go/issues/1367
• [ ] https://github.com/elastic/apm-agent-ruby/issues/1337