[DebugInfo] Add a test for dumping DWARF64 CIEs and FDEs (8/8).

This adds a test to check that Length and CIE_id/CIE_pointer fields in
.debug_frame section are printed as 16-digit hex values if the records
are in the DWARF64 format.

Differential Revision: https://reviews.llvm.org/D79997