Make raw2trace more isolated

Created by: s-kanev

Right now, it aborts on error and uses global options. Fix that.

Also, it does a lot of directory walking and raw IO, which doesn't work with more exotic filesystems, where we can be storing very large traces. Split out a self-contained library, which:

• only takes already opened std::istream and std::ostream-compatible files and doesn't own them;
• takes in the contents of the module file to avoid doing IO from drmodtrack_offline_read();
• returns errors on failure;
• doesn't depend on dr_frontend.

Also, add a frontend helper, which preserves the current behavior for local use on regular POSIX and Windows.