[Core]Change the log level of key placement group logs to facilitate troubleshooting of PG-related issues

[larrylian]

Why are these changes needed?

• The preparing resource and committing resource stages are time-consuming and often error-prone stages during PG creation. Therefore, these logs are critical for troubleshooting slow PG scheduling and PG scheduling errors in production environments.
• Currently, the key logs for PG scheduling are set to DEBUG level, which results in limited logs available for troubleshooting PG scheduling issues in production environments.
• The logs that I modified will not be frequently printed.

Related issue number

Checks

• [x] I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• [x] 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 :(