[clang] [serialization] no transitive decl change (PR #92083)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

I sent https://github.com/llvm/llvm-project/pull/95348 for aligned related change.

For size increase, the reason and the possible solution are clear. We should store the declaration ID as two slots instead of one in the serialized format so that we can utilize VBR6 format better.

https://github.com/llvm/llvm-project/pull/92083