Add support for structured debug stores in OrbitService
Add support for structured debug stores in OrbitService

This extends OrbitSerice's mechanism for finding debug info and symbol
files. In addition to checking a variety of search paths, it will also
check the local structured symbol store `/usr/lib/debug`. This helps
with finding symbols for system libraries like `libc-2.24.so`.

google/orbit,google/orbit,google/orbit,google/orbit