refactor(ray_plugin): remove runtime_env from RayJobConfig

[pingsutw]

Although Ray can install Python packages at runtime, we should encourage users to build the image at compile time using imageSpec.

Note: Also find a bug while using runtime_env with the latest ray.

2024-06-10 21:42:03,280 INFO cli.py:304 -- Tailing logs until the job exits (disable with --no-wait):

Traceback (most recent call last):
  File "/usr/local/bin/pyflyte-execute", line 8, in <module>
    sys.exit(execute_task_cmd())
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/flytekit/bin/entrypoint.py", line 506, in execute_task_cmd
    _execute_task(
  File "/usr/local/lib/python3.10/site-packages/flytekit/exceptions/scopes.py", line 148, in f
    return outer_f(inner_f, args, kwargs)
  File "/usr/local/lib/python3.10/site-packages/flytekit/exceptions/scopes.py", line 178, in system_entry_point
    return wrapped(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/flytekit/bin/entrypoint.py", line 379, in _execute_task
    _task_def = resolver_obj.load_task(loader_args=resolver_args)
  File "/usr/local/lib/python3.10/site-packages/flytekit/core/utils.py", line 306, in wrapper
    return func(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/flytekit/core/python_auto_container.py", line 252, in load_task
    task_module = importlib.import_module(name=task_module)  # type: ignore
  File "/usr/local/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/root/ray_plugin/ray_example.py", line 47, in <module>
    @ray.remote
NameError: name 'ray' is not defined
2024-06-10 21:42:20,667 ERR cli.py:68 -- --------------------------------------------
2024-06-10 21:42:20,668 ERR cli.py:69 -- Job 'a6j6hhs26x5rksq8x4r5-n0-0-65w78' failed
2024-06-10 21:42:20,668 ERR cli.py:70 -- --------------------------------------------
2024-06-10 21:42:20,668 INFO cli.py:83 -- Status message: Job entrypoint command failed with exit code 1, last available logs (truncated to 20,000 chars):
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/root/ray_plugin/ray_example.py", line 47, in <module>
    @ray.remote
NameError: name 'ray' is not defined