[clang] [Serialization] Load Specializations Lazily (PR #76774)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> [do not merge] [runtime-cxxmodules] Rework our lazy template specialization deserialization mechanism root-project/root#14495

>From https://github.com/root-project/root/pull/14495, I see there is new reply saying the testing is actually fine. Do you think we still need to split the patch?

https://github.com/llvm/llvm-project/pull/76774