Use and export proguard flags from static dependencies

Export proguard flags from Android library modules, and use them
from static dependencies in Android apps when running proguard.
Also export them to Make.

Unlike Make, which concatentates all the exported flags from
dependencies, Soong dedups exported flags files.

Bug: 73724997
Test: m checkbuild
Change-Id: I8f86fecb09cbc591832ce67e8ecef551a6600349
Merged-In: I8f86fecb09cbc591832ce67e8ecef551a6600349
(cherry picked from commit 89c31581)