Expose DeviceProtos' paths to parse in Framework

Framework currently hardcodes the paths to flags protos, with
this change it will be able to reuse the globally defined ones
and also gets access to all APEX flags

Bug: 301491148
Test: build + boot
Flag: EXEMPT build change
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:1e85e40c3ead83585ac3d7c71a712d35cd420a36)
Merged-In: I91dae72c32c47888697914265c90918389aa4c25
Change-Id: I91dae72c32c47888697914265c90918389aa4c25