[NFC] [C++20] [Modules] [Reduced BMI] Reorder Emitting reduced BMI and normal BMI for named modules

When we generate the reduced BMI on the fly, the order of the emitting
phase is different within `-emit-obj` and `-emit-module-interface`.
Although this is meant to be fine, we observed it in
https://github.com/llvm/llvm-project/issues/93859 (that the different phase order may cause problems).
Also it turns out to be a different fundamental reason to the orders.

But it might be fine to make the order of emitting reducing BMI at first
to avoid such confusions in the future.