[clang] [clang][CFG] Sequence RHS before LHS for overloaded assignment operators in CFG to match C++17 rules (PR #181113)

[Utkarsh Saxena via cfe-commits]

https://github.com/usx95 approved this pull request.

Thanks. LGTM. Some nits inline.

https://github.com/llvm/llvm-project/pull/181113