performDexOptLibsLI and related methods were extracted to PackageDexOptimizer
class. Minor refactoring of PackageManagerService.
This is a non-functional change. It should simplify further work to allow
storing OAT files inside package dir.
(cherry picked from commit eeea67b8c3)
Change-Id: I3494a2da70605362bb6fb4625ffbee1cbe1cd457