Add integration test for Docker executor to check each step is executed

Overview

In gitlab#215037 (closed) we had a regression where the after_script was not running inside of the docker executor. This has shown a test gap in out integration tests for the Docker executor, we aren't making sure that each section/stage of the job is being executed.

Proposal

Update tests like TestDockerCommandSuccessRun, TestDockerCommandBuildFail and validate that each stage runs:

• before_script
• script
• after_script

Other steps should be validated in a follow-up issue #26839