Use FeatureFlagPersistent to guard DynamicSystem

Check persistent feature flag 'settings_dynamic_system' before
invoking the installation service. User can still use gsi_tool if
the device is unlocked.

Bug: 119647479
Test: Verified with 'adb shell am' and test app.
Change-Id: If2265d877bc7eedf9b7a107bba04d2e95cf1b89a