[DWARFYAML] Add emitDebug[GNU]Pub[names/types] functions. NFC.

In this patch, emitDebugPubnames(), emitDebugPubtypes(),
emitDebugGNUPubnames(), emitDebugGNUPubtypes() are added.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D85003