[Serve] Modify max_concurrency in actor options to respect max_ongoing_requests (#47681)

[akyang-anyscale]

Why are these changes needed?

This PR modifies the actor_options used when deploying replicas. Deployment will use the configured max_ongoing_requests attribute of the deployment config as the replica's max_concurrency if
the concurrency is not explicitly set. This is to prevent replica's max_concurrency from capping
max_ongoing_requests.

Related issue number

Closes #47681

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 :(

[zcin]

Nice work! were you able to test this e2e manually?

[zcin]

ray_actor_options is limited to a structured schema RayActorOptionsSchema, which doesn't allow max_concurrency, so I think you don't need to check for max_concurrency

[akyang-anyscale]

yeah this was trying to future proof

[zcin]

Suggested change

	# Default max_concurrency option in @ray.remote for aysnc actors.
	# Default max_concurrency option in @ray.remote for async actors.

[akyang-anyscale]

Yes tested with the script provided in the issue

from ray import serve
from ray.serve.handle import DeploymentHandle
import asyncio

@serve.deployment(max_ongoing_requests=4096)
class Model:
    @serve.batch(max_batch_size=2048, batch_wait_timeout_s=2)
    async def __call__(self, ls: list[int]) -> list[int]:
        print(f"Length of input list: {len(ls)}")
        return ls

async def main() -> None:
    handle: DeploymentHandle = serve.run(Model.bind())
    await asyncio.gather(*[handle.remote(i) for i in range(2048)])

if __name__ == "__main__":
    asyncio.run(main())

Before:

$ python test.py
Length of input list: 1000 
Length of input list: 1000 
Length of input list: 48

After:

$ python test.py
Length of input list: 2048

[zcin]

@akyang-anyscale lint is failing