[BOLT][DWARF] Move line info emission into BOLT

Summary:
BOLT needs to generate line info tables using absolute addresses as well
as using the standard MC way of labels attached to instructions. Move
line table generation code under BOLT.

Ideally, we should be able to extend existing interfaces in LLVM, but
without other users of the interface it will be hard to justify the
change.

(cherry picked from FBD30723466)