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

[Vassil Vassilev via cfe-commits]

vgvassilev wrote:

> > [do not merge] [runtime-cxxmodules] Rework our lazy template specialization deserialization mechanism [root-project/root#14495](https://github.com/root-project/root/pull/14495)
> 
> From [root-project/root#14495](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?

That comment was concerning the version of the patch that had the lazy template deserialization turned off by default. Yes, I still think that this patch should implement tha on-disk hash table on top of D41416

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