W2530 (SnapStart): recognize AutoPublishAlias on AWS::Serverless::Function

[kddejong]

Follow-up to #4491. Tracked in #4607.

Problem

Two gaps. (1) W2530 keyword path is AWS::Lambda::Function/Properties/SnapStart/ApplyOn only. (2) Its check looks for an attached AWS::Lambda::Version via get_resource_children, which SAM no longer synthesizes from AutoPublishAlias. So SnapStart on a SAM function is unchecked.

Fix

Add the AWS::Serverless::Function keyword path AND treat AutoPublishAlias on the SAM function as satisfying the version-attached condition (instead of hunting for a synthesized AWS::Lambda::Version).

Acceptance

• SAM function with SnapStart enabled + AutoPublishAlias -> no error
• SnapStart enabled without a version/alias -> W2530
• fixtures + unit test

[DomDriverCoop]

Think I'm seeing possible related behaviour here even without snapstart enabled. Lambda function definition in SAM template:

LambdaFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: index.handler
      Runtime: python3.13
      AutoPublishAlias: live
     ...

References to the integer Version property of the generated AWS::Lambda::Version resource in Cloudwatch alarm definitions (for example):

      - Name: ExecutedVersion
        Value: !GetAtt LambdaFunction.Version.Version

Now result in this error:

E1010 'Version.Version' is not one of ['SnapStartResponse', 'SnapStartResponse.ApplyOn', 'SnapStartResponse.OptimizationStatus', 'Arn'] in ['us-east-1']
module/template.sam.yaml:269:9

Intention is that the integer version value is returned. Deployment succeeds and assigns the version value correctly, even though linting fails.