[Train] Improve loggings for Train worker scheduling information

[woshiyyya]

Why are these changes needed?

Currently, the placement and ranking information of distributed process groups in the log is unclear. Users must manually print out the world ranking, local ranking, and node IP. This PR improves log messages with more placement information to improve observability and debuggability.

Previous:

(TorchTrainer pid=7236) Starting distributed worker processes: ['7410 (10.0.59.242)', '7411 (10.0.59.242)', '7412 (10.0.59.242)', '7413 (10.0.59.242)', '3381 (10.0.12.174)', '3382 (10.0.12.174)', '3383 (10.0.12.174)', '3384 (10.0.12.174)']

Now:

(TorchTrainer pid=7236) Started distributed worker processes: 
(TorchTrainer pid=7236) - (ip=10.0.59.242, pid=7410) rank=0, local_rank=0, node_rank=0
(TorchTrainer pid=7236) - (ip=10.0.59.242, pid=7411) rank=1, local_rank=1, node_rank=0
(TorchTrainer pid=7236) - (ip=10.0.59.242, pid=7412) rank=2, local_rank=2, node_rank=0
(TorchTrainer pid=7236) - (ip=10.0.59.242, pid=7413) rank=3, local_rank=3, node_rank=0
(TorchTrainer pid=7236) - (ip=10.0.12.174, pid=3381) rank=4, local_rank=0, node_rank=1
(TorchTrainer pid=7236) - (ip=10.0.12.174, pid=3382) rank=5, local_rank=1, node_rank=1
(TorchTrainer pid=7236) - (ip=10.0.12.174, pid=3383) rank=6, local_rank=2, node_rank=1
(TorchTrainer pid=7236) - (ip=10.0.12.174, pid=3384) rank=7, local_rank=3, node_rank=1

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 :(

[matthewdeng]

@scottsun94 can you leave your thoughts? Originally we wanted to keep it succinct but found that it is not sufficient for users to debug certain issues.

[scottsun94]

LGTM. Since it only shows up once (unless there are location changes), it's fine to be a bit more verbose.

[scottsun94]

LGTM. Thanks!