Flag off RAY_legacy_scheduler_warnings

[ericl]

Why are these changes needed?

Disable the legacy scheduler warnings, per #18724

[rkooo567]

Lgtm!

Btw once infreasible task exception is supported, I want to revive error msg from raylet. The reason is primarily because the quality of error msg will be a lot better if this is printed from raylet (e.g., we can print the name of task that’s hanging). In this case, we can get the best of the both worlds (not printing msg when autoscaling + better error msg)

alternatively, we can report function names to gcs. I think we can discuss what’s better when this actually happens

[bveeramani]

‼️ ACTION REQUIRED ‼️

We've switched our code formatter from YAPF to Black (see #21311).

To prevent issues with merging your code, here's what you'll need to do:

1. Install Black

pip install -I black==21.12b0

2. Format changed files with Black

curl -o format-changed.sh https://gist.githubusercontent.com/bveeramani/42ef0e9e387b755a8a735b084af976f2/raw/7631276790765d555c423b8db2b679fd957b984a/format-changed.sh
chmod +x ./format-changed.sh
./format-changed.sh
rm format-changed.sh

3. Commit your changes.

git add --all
git commit -m "Format Python code with Black"

4. Merge master into your branch.

git pull upstream master

5. Resolve merge conflicts (if necessary).

After running these steps, you'll have the updated format.sh.