The ResourceManager interface can be used to implement ownership for resources
allocated to JIT'd code, e.g. memory and metadata registrations (frame info,
language runtime metadata, etc.).
Resources can be *deallocated*, meaning that they should be cleaned up (memory
released, registrations deregistered, etc.), or they can be *detached*, meaning
that cleanup should be performed automatically when the ResourceManager itself
is destroyed.
The intent is to allow JIT'd code to continue running after the
llvm::orc::ExecutionSession that produced it is disconnected / destroyed.
