[ORC] Add EPCGenericJITLinkMemoryManager::Create named constructor. (#188191)
Create takes a JITDylib and a SymbolNames struct, looks up the
implementation symbol addresses in the given JITDylib, and uses them to
construct an EPCGenericJITLinkMemoryManager instance. This makes it
easier for ORC clients to construct the memory manager from named
symbols (e.g. in a bootstrap JITDylib) rather than raw addresses.