[DWARFYAML] Teach yaml2obj emit the correct line table program.

The following issues are addressed in this patch.

1. The operands of DW_LNE_set_discriminator should be an ULEB128 number
   rather than an address.
2. Test the emitted opcodes.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D85717