Implemented AWS lambda spec changes

[AlexanderWert]

• Fixes Fix Lambda Instrumentation for non existent status code #2346
• Implements [META 584] Implement changes on AWS lambda context capturing #2394
  • 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).
• Send empty request with flushed=true query param on Lambda data flush ([META 569] Add query param flushed=true to final intake request at the end of lambda function #2305)
• Update docs:
  • Remove the experimental flag from the Lambda feature
  • Add something about potential long start and possible configurations - enable_instrumentations, increasing timeout, increasing heap size

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• Start Time: 2022-03-15T13:09:57.748+0000

• Duration: 49 min 6 sec

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Total	2776

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/test

[eyalkoren]

Looks good!
Missing:

• Serialization test for faas fields (id, name, version)
• Tests for faas.name and faas.version correctness in the Lambda tests

Let's sort out our transaction naming approach offline and I will make adjustments if required and implement #2305

[AlexanderWert]

I reviewed the changes.
Except a small bug, that I found in my own code, everything looks good.

Tested the interplay with the extension: The extension receives the flush=true signal as expected. So all good on that side as well.