[clang] [Clang] Generate the GEP instead of adding AST nodes (PR #73730)

[Nick Desaulniers via cfe-commits]

https://github.com/nickdesaulniers commented:

Hey, that looks pretty good!  I'm surprised it wasn't too much more work to convert to generating the GEP directly. Nice job!

Does this change result in codegen differences in IR? (was expecting test changes that used "fork" loads and "bork" GEPs)

https://github.com/llvm/llvm-project/pull/73730