Consider removing `CallExpr::CreateTemporary`

[HighCommander4]

Filing this issue to track a suggestion made by @cor3ntin in this comment:

I wonder if we could get rid of CallExpr::CreateTemporary and instead
create something like an OpaqueValueExpr for the purpose of determining an initialization sequence.

(We should only need some expression with a type, a location, and a value category, afaik)

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Nathan Ridge (HighCommander4)

Filing this issue to track a suggestion made by @cor3ntin in [this comment](https://github.com//pull/130725#pullrequestreview-2673499083):

> I wonder if we could get rid of CallExpr::CreateTemporary and instead
create something like an OpaqueValueExpr for the purpose of determining an initialization sequence.
>
> (We should only need some expression with a type, a location, and a value category, afaik)