[clang] [CIR] Make LLVM & OGCG variables match the same pattern (PR #135427)

[Amr Hesham via cfe-commits]

AmrDeveloper wrote:

> To clarify I wasn't saying that the LLVM checks and OGCG checks needed to use the same patterns/names (though it's nice that they do now). The important thing was not to have the value identifiers hard-corded in the checks.
> 
> Thanks for the update!

I found that it easier to understand both if they are named with the same pattern, for example in the 2D Array index expression it's more clear now :D

Thank you

https://github.com/llvm/llvm-project/pull/135427