[ORC] Generalize emit re-entry, stub, etc. APIs for working addr != link addr.

[ORC] Generalize emit re-entry, stub, etc. APIs for working addr != link addr.

This patch generalizes the APIs for writing re-entry blocks, trampolines and
stubs to allow their final linked address to differ from the address of
their initial working memory. This will allow these routines to be used with
JITLinkMemoryManagers, which will in turn allow for unification of code paths
for in-process and cross-process lazy JITing.