[clang] [NFC][Clang] Introduce type aliases to replace use of auto in clang/lib/CodeGen/CGCall.cpp. (PR #135861)

[Aaron Ballman via cfe-commits]

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

LGTM! We could do further coding style adjustments if we wanted (particularly around naming conventions), but I don't insist; this is still forward progress. Thank you!

https://github.com/llvm/llvm-project/pull/135861