[llvm] [LLVM] Create `lf_alias` nodes for `typedef` and `using` (PR #153936)

[via llvm-commits]

Nerixyz wrote:

> I'll still probably be busy for another month or so, so if anyone wants to yoink these changes and/or implement this themselves, feel free.

Opened https://github.com/llvm/llvm-project/pull/218243 to implement the first part of this.

https://github.com/llvm/llvm-project/pull/153936