Remove Service Override from aws.lambda spans

[zarirhamza]

What does this PR do?

Change the lambda span service name priority:

1. value of DD_SERVICE
2. value of lambda function name
3. aws.lambda

Also changes cold_start values to true/false

Motivation

Removes service overrides for aws.lambda span

Testing Guidelines

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

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[astuyve]

I don't think this can ship. Many assumptions are made in the backend based on this

[zarirhamza]

I don't think this can ship. Many assumptions are made in the backend based on this

What part exactly is blocking? Is it changing the service name from aws.lambda to functionName? That change was already merged in #655. The only thing to look out for was span.name according to Rey and that is different from serviceName. The property span.name is akin to operation name which is unchanged with these changes.

Or is it respecting the DD_SERVICE env var specifically for lambda spans? That isn't really changing any behavior because the rust extension already does that. This change simply performs that renaming earlier in the life of the trace so that base_service is not on the tracer leading to indications of a service override on the UI even though the base_service and actual service are the same.

[zarirhamza]

Reminder - Use this PR to collapse cold start to use Boolean values