[Orc] Use MapperJITLinkMemoryManager with SharedMemoryMapper in llvm-jitlink tool

MapperJITLinkMemoryManager combined with SharedMemoryMapper can be
used in place of EPCGenericJITLinkMemoryManager when running on top of
same physical memory. This commit enables it when --use-shared-memory is
passed.

Differential Revision: https://reviews.llvm.org/D132369