Move all config constants into single file. (#1192)

* Initial pass at factoring out C++ configuration into a single file.

* Expose config through Python.

* Forward declarations.

* Fixes with Python extensions

* Remove old code.

* Consistent naming for constants.

* Fixes

* Fix linting.

* More linting.

* Whitespace

* rename config -> _config.

* Move config inside a class.

* update naming convention

* Fix linting.

* More linting

* More linting.

* Add in some more constants.

* Fix linting

python/ray/__init__.py

@@ -40,6 +40,7 @@ except ImportError as e:
             e.args += (helpful_message,)
     raise
 
+from ray.local_scheduler import _config  # noqa: E402
 from ray.worker import (error_info, init, connect, disconnect,
                         get, put, wait, remote, log_event, log_span,
                         flush_log, get_gpu_ids, get_webui_url,
@@ -59,7 +60,7 @@ __all__ = ["error_info", "init", "connect", "disconnect", "get", "put", "wait",
            "remote", "log_event", "log_span", "flush_log", "actor",
            "get_gpu_ids", "get_webui_url", "register_custom_serializer",
            "SCRIPT_MODE", "WORKER_MODE", "PYTHON_MODE", "SILENT_MODE",
-           "global_state", "__version__"]
+           "global_state", "_config", "__version__"]
 
 import ctypes  # noqa: E402
 # Windows only