Remove .circleci folder (#13232)

Summary:
Originally I was trying to update `build-linux-clang10-mini-tsan` to actually use `clang10` (as the name implied). #13220 was supposed to also update this configuration, but I did not see that we had a definition for `build-linux-clang10-mini-tsan` in both `config.yml` and `pr-jobs.yml`. I was wondering why I could not see my changes reflected in the CI checks after merging. After I updated `pr-jobs.yml` for this PR, I found that the CI check started failing https://github.com/facebook/rocksdb/actions/runs/12417441052/job/34668411263?pr=13232. I don't think it makes sense for me to tackle looking into all the TSAN warnings being reported in `clang10` (at least in this PR), so for now I have updated the name of the PR job to accurately reflect the command that is being run.

This PR also gets rid of the entire `.circleci` folder, which I think is the more significant change.

Pull Request resolved: #13232

Test Plan: Existing CI check is unchanged

Reviewed By: pdillinger

Differential Revision: D67462454

Pulled By: archang19

fbshipit-source-id: f1aabfe4c8793616d6cbaae36fdf007319bf7ab2