[ORC] Rename 'finalize' to 'emit' to avoid potential confusion.

An emitted symbol has had its contents written and its memory protections
applied, but it is not automatically ready to execute.

Prior to ORC supporting concurrent compilation, the term "finalized" could be
interpreted two different (but effectively equivalent) ways: (1) The finalized
symbol's contents have been written and its memory protections applied, and (2)
the symbol is ready to run. Now that ORC supports concurrent compilation, sense
(1) no longer implies sense (2). We have already introduced a new term, 'ready',
to capture sense (2), so rename sense (1) to 'emitted' to avoid any lingering
confusion.

llvm-svn: 340115