[lldb/Disassembler] Move address resolution into the ParseInstructions function

The static Disassembler can be thought of as shorthands for three
operations:
- fetch an appropriate disassembler instance (FindPluginForTarget)
- ask it to dissassemble some bytes (ParseInstructions)
- ask it to dump the disassembled instructions (PrintInstructions)

The only thing that's standing in the way of this interpretation is that
the Disassemble function also does some address resolution before
calling ParseInstructions. This patch moves this functionality into
ParseInstructions so that it is available to users who call
ParseInstructions directly.