Add qa test users to delete user projects script

What does this MR do and why?

Updates delete_user_projects script to accept the environment variable CLEANUP_ALL_QA_USER_PROJECTS and adds a list of qa test user usernames that are the same across environments. We can't hardcode or pass the ids because they are different on the live environments that this script runs on, therefore they need to be fetched by the username for each. This change allows USER_ID and/or CLEANUP_ALL_QA_USER_PROJECTS to be used separately or together for greater flexibility.

Part of gitlab-org/quality/quality-engineering&24 and gitlab-org/quality/quality-engineering/team-tasks#1477 (closed)

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