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### What does this PR do?
<!--- A brief description of the change being made with this pull
request. --->

Rollout of span naming changes to align serverless product with tracer
to create streamlined Service Representation for Serverless

Key Changes:

- Change service name to match instance name for all managed services
(aws.lambda -> lambda name, etc) (breaking)
- Opt out via `DD_TRACE_AWS_SERVICE_REPRESENTATION_ENABLED`

- Add `span.kind:server` on synthetic spans made via span-inferrer, cold
start and lambda invocation spans

- Remove `_dd.base_service` tags on synthetic spans to avoid
unintentional service override

### Motivation

<!--- What inspired you to submit this pull request? --->

Improve Service Map for Serverless. This allows for synthetic spans to
have their own service on the map which connects with the inferred spans
from the tracer side.