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

[Teresa Johnson via llvm-commits]

https://github.com/teresajohnson commented:

This change looks fine but see my comment on PR88024 for a suggestion on testing for this one (moving a couple things from that patch to this one and submitting this one second). 

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