Doc for testing and code coverage

docs/dev_tools/test.md

docs/files/screenshots/settings_php_interpreter.png

docs/files/screenshots/settings_php_interpreter_docker.png

docs/files/screenshots/settings_php_interpreter_new.png

docs/files/screenshots/settings_php_test_coverage_view.png

docs/files/screenshots/settings_php_test_execution.png

docs/files/screenshots/settings_php_test_framework_new.png

...es/screenshots/settings_php_test_framework_new_config.png

docs/new-features.md

docs/versions.txt