[clang] [clang] Represent array refs as `TemplateArgument::Declaration` (PR #80050)

[Andrey Ali Khan Bolshakov via cfe-commits]

bolshakov-a wrote:

> what a proper fix would look like

Probably, some more `OpaqueValueExpr` handlers should be rewritten correctly.

https://github.com/llvm/llvm-project/pull/80050