[llvm] [ThinLTO][BitcodeWriter] Write import type in per-module combined summary (PR #87600)

[Mingming Liu via llvm-commits]

minglotus-6 wrote:

thanks for the reviews @jvoung ! I'll hold this patch and plan to land this together with the follow-up one (https://github.com/llvm/llvm-project/pull/88024), primarily because regression tests are added there; meanwhile this gives time for more feedbacks :)

https://github.com/llvm/llvm-project/pull/87600