fix(instrumentation-aws-lambda): soften "unable to init" message and demote to diag.debug

[beggers]

Which problem is this PR solving?

• Fixes Unable to initialize instrumentation for lambda. Cannot identify lambda handler or task root. #1774

When not in a Lambda, the AWS Lambda instrumentation spits out an error-level message saying it can't initialize. This pollutes logs for all Node applications using autoinstrumentation.

Short description of the changes

• Switch to a debug-level message since this is an expected case.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: beggers / name: Ben Eggers (3362080, abd083b, 460d449, c9a5a54)
• ✅ login: trentm / name: Trent Mick (2e94096)

[trentm]

LGTM.

It is reasonable to have any given instrumentation enabled, even if it ends up not being relevant for the app; and is commonly the case given the current advice to use auto-instrumentations-node.

If those envvars (defined at https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html#configuration-envvars-runtime) are not set, then the app isn't in a Lambda env. In that case, it is weird to log an error about it. I'd even consider softening the language of the debug message.

[codecov]

Codecov Report

Merging #1836 (2e94096) into main (1c2e8b2) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

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  Coverage   96.06%   96.06%           
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  Files          14       14           
  Lines         914      914           
  Branches      199      199           
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  Hits          878      878           
  Misses         36       36           

[beggers]

Hey @trentm looks like CI is failing due to code coverage (0% of new lines are covered by tests, the horror). Is it cool to merge this as-is?

[trentm]

the horror

Heh.

@beggers I think it is good to go, yes. However, I'm a fairly new approver on this repo, so I was going to wait a little while to give others a chance to approve or not.

@carolabadeer You are the component owner, do you have an opinion on this PR? Thanks.