[libcxx] [llvm] [libc++] LWG3870: Remove `voidify` (PR #110355)

[Michael Buch via llvm-commits]

Michael137 wrote:

If it turns out we can't do this in the formatters, I think the best course of action to unblock this is as follows:
1. Revert https://reviews.llvm.org/D142268 (which means we emit canonical typenames into `DW_AT_name` for template aliases again). It's a nice-to-have for LLDB but is really just a workaround, and also causes the bug in the formatters, uncovered by this PR.
2. Reland this libc++ PR
3. Fix the problem in (1) by either implementing `DW_TAG_template_alias` support in LLDB and flipping the `-gtemplate-alias` default to `true` (the `DW_AT_default_value` on the template parameters should allow us to suppress the default arguments then)

https://github.com/llvm/llvm-project/pull/110355