[clang] [Clang] Apply exclude_from_explicit_instantiation to dllimport/dllexport (PR #168171)

[Tomohiro Kashiwada via cfe-commits]

kikairoya wrote:

Thank you for the merging the other PR. I'll rebase this PR onto the merged commit, with a restructuring.

https://github.com/llvm/llvm-project/pull/168171