This PR introduces parallel test execution capability to the scenarigo testing framework.

Main Feature:

• Adds a new --parallel command-line option that enables running tests concurrently per file instead of sequentially

Technical Changes:

• Reporter Interface Enhancement: Added Cleanup and Teardown methods to the Reporter interface to properly handle resource management in parallel execution contexts
• Parallel Execution Logic: Implemented the core functionality to distribute test files across multiple workers
• Resource Management: Ensures proper cleanup and teardown procedures when tests run in parallel

This enhancement allows users to significantly speed up their test execution by running test files concurrently, which is especially beneficial for large test suites.