[clang-format] Add tests for aligning `operator=` with `=delete`. NFC.

Also, add test case from https://github.com/llvm/llvm-project/issues/33044.
This was actually fixed in https://github.com/llvm/llvm-project/commit/480a1fab72f4e367a5986d572914d252c318431d, but there were no tests for delete.