[clang] [clang-format] Add KeepEmptyLines.AtEndOfBlock option (PR #224223)

[Björn Schäpers via cfe-commits]

https://github.com/HazardyKnusperkeks commented:

Please push all changes in own commits, the PR will be rebased and squashed on merge.

You may add a release note for the new option.

https://github.com/llvm/llvm-project/pull/224223