[ObjectYAML][ELF] Add support for emitting the .debug_gnu_pubnames/pubtypes sections.

This patch helps add support for emitting the .debug_gnu_pubnames and .debug_gnu_pubtypes sections.

The .debug_gnu_pub* sections is verified by llvm-dwarfdump.

Known issues:
- Doesn't support emitting multiple pub-tables.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D82367