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

[Michael Buch via llvm-commits]

Michael137 wrote:

> Looking over the code again, I don't think turning this into 3 PRs is worth it. The LLDB changes by themselves are just a [toggle switch](https://github.com/llvm/llvm-project/pull/152484/commits/3652c756341050acc0c50cb5e6f44e31538285d4) that enables LLDB to use the LLVM code from this patch. It doesn't compile without the LLVM changes because the visitor would be missing an implementation. 
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> Like it sucks that the PR isn't perfectly isolated, but the code itself isn't. LLDB and LLVM both use the same mechanism to operate on the node. If we change that mechanism we need to account for both. It's still a single end-to-end change even though it spans 2 projects.
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Is the lldb change ready to go? If so, i'll go ahead and land them all (if you dont have merge rights).

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