[clang] [WIP][Modules] Delay deserialization of preferred_name attribute at r… (PR #122726)

[Ilya Biryukov via cfe-commits]

https://github.com/ilya-biryukov commented:

I know this is marked as `WIP`, but I find the direction promising so I went ahead and actually made a round of review.

Please wait for @ChuanqiXu9 in case he'll have more comments, but I hope two of us are not too far off in terms of where we want this to go.

https://github.com/llvm/llvm-project/pull/122726