[ObjectYAML][ELF] Add support for emitting the .debug_abbrev section.

This patch enables yaml2elf emit the .debug_abbrev section.

The generated .debug_abbrev is verified using `llvm-dwarfdump`.

Known issues that will be addressed later:
- Current implementation doesn't support generating multiple abbreviation tables in one .debug_abbrev section.

Reviewed By: jhenderson, grimar

Differential Revision: https://reviews.llvm.org/D81820