Allow firmware binaries to be specified only by load address

Add support to Mach-O corefiles and to live gdb remote serial protocol
connections for the corefile/remote stub to provide a list of load
addresses of binaries that should be found & loaded by lldb, and nothing
else.  lldb will try to parse the binary out of memory, and if it can
find a UUID, try to find a binary & its debug information based on the
UUID, falling back to using the memory image if it must.

A bit of code unification from three parts of lldb that were loading
individual binaries already, so there is a shared method in
DynamicLoader to handle all of the variations they were doing.

Differential Revision: https://reviews.llvm.org/D130813
rdar://94249937
rdar://94249384