Add Dockerfile and Docker Compose for Redfish Emulator setup

[marko-stanojevic]

Description

This pull request introduces a comprehensive Redfish emulator setup for integration testing, with full documentation, Docker support, and new integration tests. The changes enable automated and local integration testing against a real Redfish API mockup, improving test reliability and developer experience.

Redfish Emulator Infrastructure:

• Added a new Dockerfile.DMTF.Redfish.Emulator to build a containerized DMTF Redfish-Mockup-Server, including health checks and configurable ports and mockup data.
• Introduced docker-compose.emulator.yml for easy local deployment of the Redfish emulator, supporting custom networks and environment variables.
• Added docs/redfish-emulator.md with detailed instructions for running the emulator, troubleshooting, and CI/CD integration.

CI/CD Integration:

• Updated .github/actions/ps-integration-tests/action.yml to start and stop a Redfish emulator container as part of the integration test workflow, ensuring the emulator is available during tests.
• Modified .github/workflows/ci.yml to invoke the new integration test action after building the module.

Integration Test Improvements:

• Added tests/Integration/Redfish.Requests.Integration.Tests.ps1, a comprehensive PowerShell Pester test suite for Redfish API requests, including environment detection, error handling, metrics, and pipeline support.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Code quality improvement (refactoring, tests, performance)