[DWARFLinker] Refactor cloneAddressAttribute().

As a preparation for implementing DWARFv5 address ranges generation,
this patch refactors cloneAddressAttribute() method. It has special
handling for addresses which can be relocated in some unrelated value,
for applying relocations twice, for indexed addresses. Instead of
all these special handlings this patch uses general handling:

Read attribute value from InputDIE and apply PCOffset.

Another thing is that current handling of DW_FORM_addrx misses the
fact that relocations might be applied twice in some cases. This
patch fixes this problem also.

Differential Revision: https://reviews.llvm.org/D143269