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

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

Update: 

Previously we will always try to load the specializations with the
    corresponding arguments before finding the specializations. This
    requires to hash the template arguments.

    This patch tries to improve this by trying to load the specializations
    only if we can't find it locally.

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