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

[Jeremiah Rodriguez via cfe-commits]

jeremiahar wrote:

This also avoids regressing https://github.com/llvm/llvm-project/issues/79957 (I cherrypicked this commit and compiled the test case locally)

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