[Core] Implement py_executable support for runtime environments to enable better UV support

[pcmoritz]

Why are these changes needed?

This implements a very simple runtime environment plugin that allows e.g. using the uv run command for dependency handling (but could also be useful for wrapping the worker command e.g. with a profiler or debugger).

Very simple example:

uv run --with emoji test.py

with

import ray

ray.init(runtime_env={"py_executable": "uv run --with emoji"})

@ray.remote
def f():
    import emoji
    return emoji.emojize("Ray rocks :thumbs_up:")

print(ray.get(f.remote()))

Slightly more complex example with pyproject.toml in the working_dir (see https://docs.astral.sh/uv/guides/scripts):

uv run test.py

with

pyproject.toml:

[project]

name = "test"

version = "0.1"

dependencies = [
   "rich",
   "emoji",
   "ray", # had to do "ray @ file:///tmp/ray-2.41.0-cp312-cp312-macosx_11_0_arm64.whl" here since this is not released yet
]

text.py

import ray
import time
from rich.progress import track

ray.init(runtime_env={"working_dir": ".", "py_executable": "uv run --isolated"})

@ray.remote
def f():
    import emoji
    return emoji.emojize("Ray rocks :thumbs_up:")

for i in track(range(20), description="For example:"):
    print(ray.get(f.remote()))
    time.sleep(0.05)

And the dependencies can also be locked with uv lock.

Related issue number

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[edoakes]

Looks good pending uv e2e test

[edoakes]

👍