Add end-to-end integration tests

[fabisev]

Add end-to-end integration tests for aws-lambda-java-log4j2
Adds integration tests that deploy a Lambda function using aws-lambda-java-log4j2, invoke it, and verify logs arrive in CloudWatch. This catches the main regression path: Log4j2 plugin discovery failing due to a missing Log4j2Plugins.dat in the shaded JAR.

• lambda-integration-tests/ - SAM project with a minimal Java Lambda function that logs a unique marker at INFO/DEBUG/WARN/ERROR levels via Log4j2 LambdaAppender
• run-tests.sh - invokes the function and polls CloudWatch to verify the marker arrived
• build-integration-test.yml - PR gate that verifies the test function compiles
• run-integration-test.yml - deploys to AWS, runs the test, cleans up

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[darklight3it]

Same here the test should be run for most packages, at least the one that are involved.

core, serialization, runtime-interface-client, log4j and i would also add events.

[darklight3it]

Same here and in all other references to github actions.

[darklight3it]

add the commit sha to prevent supply chain attacks.

[darklight3it]

For the moment it's sufficient like this but we probably can do something more advanced. For example we can create a Java project that uses a something like JUNIT to run the AWS SDK invoke the function and then get the logs.

In this way we avoid doing scripting and we can also have a nice report for how the test has gone.

[maxday]

let's make sure we run integ test on both architectures. You can use a matrix job to do this (ie: https://github.com/aws/aws-lambda-ruby-runtime-interface-client/blob/main/.github/workflows/integration-tests.yml#L32)

[darklight3it]

LGTM 🚀