[clang] [clang][Index][USR] Generate USRs for class-type non-type template arguments (PR #212356)

[Balázs Benics via cfe-commits]

steakhal wrote:

Why is this nominated to `release/23.x`?
According to the [backport criterias](https://llvm.org/docs/HowToReleaseLLVM.html#release-patch-rules) only bug fixes can be merged and this counts to me as a new feature - albeit one could argue it's a "fix" in some way.
Pre clang-23 I think the rules were more relaxed before the final releases - that we havent' reached yet upstream (we are at rc1).

https://github.com/llvm/llvm-project/pull/212356