Enforce non-null PackageSetting for PackageInfoUtils

Now that ENABLE_FEATURE_SCAN_APEX is finalized, the legacy branch
in PackageInfoUtils that allowed a nullable PackageSetting can be
removed, enforceing non-null and ensuring that state is always
available through the PackageSetting, as it is impossible to have
a valid AndroidPackage without a wrapping PackageState (although
the reverse is still possible).

Test: atest CompatibilityModeTest
Test: atest PackageParserTest
Test: atest PackageParserLegacyCoreTest

Change-Id: Id89fb766f91816b5c2e1ec94ab84cc0a7214a2a9