most of the scripts were used for Phabricator integration that is now disabled and current scripts are located in `llvm-project/.ci` . Also removed obsolete playbooks and scripts that were not used and likely no longer work. Updated wording and minor typos.
I have tried to look through potential references to the scripts and disabled some of buildkite pipelines that referred to them. That is not a guarantee that this will not break anything as I have not tried to rebuild containers and redeploy cluster.
