[Reland][DWARFLinkerParallel] Add limited functionality to DWARFLinkerParallel.

This patch is extracted from D96035, it adds support for the existing
DWARFLinker functionality. What is not supported yet:

1. Types deduplication(--odr mode).
2. Modules deduplication.
3. Generation of index tables.

Differential Revision: https://reviews.llvm.org/D153268