[ansh-rohilla]

Description

Previously, messaging.batch.message_count was set unconditionally on AWS Lambda streaming spans, defaulting to 1 for any non-list event (HTTP, S3, etc.) and len(event) for top-level lists. Moreover, SQS and SNS deliveries in AWS Lambda come as a dictionary with a Records list, so a batch of 10 messages incorrectly reported 1.

This PR:

• Adds _get_messaging_batch_count(aws_event) to identify recognized messaging services (AWS SQS and SNS) by checking whether Records is present and belongs to SQS or SNS.
• Only sets messaging.batch.message_count on the span when the invocation event is a recognized messaging batch (SQS/SNS).
• Ensures batch_size (and consequently scope.set_tag("batch_size", ...) and scope.set_tag("batch_request", True)) reflects the number of records for SQS and SNS events.
• Updates existing non-messaging tests and adds new unit tests verifying SQS, SNS, S3, DynamoDB, Kinesis, HTTP, and top-level list handling.

Issues

• resolves: fix(aws-lambda): Only set messaging.batch.message_count for messaging batches #8078
• resolves: PY-3015

[pabloDeputter]

Thanks for picking this up! Closing this for now, since we aren't sure yet how we're gonna implement this.

For now there the new tests seem to test private helpers as well as mocks; it would be better to e.g. parameterize test_span_streaming_no_error() and drop the new test_aws_lambda_messaging.py file.