[XCOFF][AIX] Generate LSDA data and compact unwind section on AIX

Summary:
AIX uses the existing EH infrastructure in clang and llvm.
The major differences would be
1. AIX do not have CFI instructions.
2. AIX uses a new personality routine, named __xlcxx_personality_v1.
   It doesn't use the GCC personality rountine, because the
   interoperability is not there yet on AIX.
3. AIX do not use eh_frame sections. Instead, it would use a eh_info
section (compat unwind section) to store the information about
personality routine and LSDA data address.

Reviewed By: daltenty, hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D91455