Move ADPF to standalone lib

Refactor the PowerAdvisor into its own independent library to better
reflect ownership and team structure, as well as making it easier to
expand and test, as the previous placement under "DisplayHardware"
was confusing.

Test: libpoweradvisor_test
Test: libsurfaceflinger_unittest
Bug: 369692284
Flag: EXEMPT refactor

Change-Id: I51388d0143b7e78413995d9c3a9bde69ae43eff2