[clang] [clang] Implement P2582R1: CTAD from inherited constructors (PR #98788)

[Haojian Wu via cfe-commits]

hokein wrote:

> I like 1, but not really 2, I think we should wait for this to be reasonably complete before merging it, particularly this close to the release. I'd probably be ok with 2 if we wait a few weeks until after the release, so that we can deal with the fallout with less stress, and fix it before Clang21 release.

+1. Rushing a new feature just before the release increases the risk of issues and adds unnecessary stress.

I believe we should find a way to land this patch, even if it’s not fully complete (it has been pending for months). Landing it after the release cut seems like a good approach. This would allow for incremental development while giving us more time to address any fallout before clang 21.

https://github.com/llvm/llvm-project/pull/98788