[lldb][LocateModuleCallback] Update SBFileSpec/SBModuleSpec

RFC https://discourse.llvm.org/t/rfc-python-callback-for-target-get-module/71580

SBFileSpec and SBModuleSpec will be used for locate module callback as Python
function arguments. This diff allows these things.
- Can be instantiated from SBPlatform.
- Can be passed to/from Python.
- Can be accessed for object offset and size.

Differential Revision: https://reviews.llvm.org/D153733