[BOLT][DWARF] Reuse entries in .debug_addr when not modified

In some binaries produced with ThinLTO there are CUs that share entry in
.debug_addr. Before we would generate a new entry for each. Which lead to binary
size increase. This changes the behavior so that we re-use entries in
.debug_addr.

Reviewed By: maksfb

Differential Revision: https://reviews.llvm.org/D142425