Spec PRs:

• Changes to lambda context capturing based on more tests and user feedback apm#579
• Added capturing of faas.name apm#603

Changes

• Change transaction.name for API Gateway-triggered Lambda functions: To be consistent with other HTTP-based instrumentations include the low-cardinality resourcePath into the name.
• Respect setting for use_path_as_transaction_name: If use_path_as_transaction_name is enabled use the full HTTP path for the transaction.name in API Gateway-triggered Lambda functions.
• Respect service_name and service_version agent config options: If service_name and/or service_version are explicitly configured use the configured values instead of the derived ones.
• Use the full domain name of the API Gateway as service.origin.name
• Replaced service.id metadata field with new transaction-level field faas.id: To being able to capture different Lambda function ARN values (semantically correct) under one APM service umbrella (for the scenario of consolidating multiple lambda functions in one APM service).
• Capture faas.name and faas.version