VCST-4552: Add workflow using Docker test environment

[AndrewEhlo]

Note

Introduces manual, Docker-based test workflows and a backend package manifest for reproducible test environments.

• Adds e2e-tests-docker.yml using reusable e2e-autotests.yml with inputs for frontendZipUrl and customPackagesJsonUrl
• Adds graphql-tests-docker.yml using reusable ui-autotests.yml with Docker tag and frontendZipUrl input
• Adds backend-packages.json defining platform image/tags and module versions, consumed by the Docker E2E workflow
• Minor whitespace-only change in existing e2e-tests.yml artifact step

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