Add comprehensive validation tests for various tools and introduce Codecov configuration (#76)

- Implemented validation tests for the following tools:
  - get_service_logs
  - run_services
  - set_environment_variable
  - get_environment_variables
  - restart_service
  - stop_services
  - check_requirements
  - install_dependencies
  - Added context cancellation test for get_service_logs tool
  - Added tests for handling azure.yaml resource and missing file scenarios
  - Added tests for project directory fallback logic

- Introduced a new Codecov configuration file to manage coverage thresholds and reporting.

Author: jongio

cli/.gitignore

@@ -2,3 +2,8 @@
 bin/
 dist/
 azd-app
+
+# Coverage output files
+cov
+mcpcov
+*.out