Add unwind info to core dumps. (#13547)

Add unwind info to core dumps. (#13547)

The createdump utility now enumerates all the native stack frames (with
some help from the managed stack walker) for all the threads adding all
the ELF unwind info needed.

On a different machine and without any of the native modules loaded when
the crashdump was generated all the thread stacks can still be unwound
with lldb/gdb.

Change the PAL_VirtualUnwindOutOfProc read memory adapter in DAC
to add the memory to instances manager.

Some misc. cleanup.