Add new dexopt flag to control hidden API restrictions

Allow PackageDexOptimizer to select which APKs should be exempt
from hidden API restrictions by creating a new DEXOPT_ flag and
passing a suitable command line argument to dex2oat if it is set.

Bug: 64382372
Test: installd_dexopt_test
Change-Id: I86917c357ced7fa04d8bb500669b76bbd4c08f2c