Adds per-app categories to untrusted app domains and their
app data types. Per-app categories are in addition to the
existing per-user categories.

Apps targeting sdk version 28+ will now have the following
characteristics:
Domain: u:r:untrusted_app:s0:c[0-9]+,c[0-9]+,c[0-9],c[0-9]
Data context: u:object_r:app_data_file:s0:c[0-9]+,c[0-9]+,c[0-9],c[0-9]

Whereas apps targeting 27- will look like:
Domain: u:r:untrusted_app_27:s0:c[0-9]+,c[0-9]+
Data context: u:object_r:app_data_file:s0:c[0-9]+,c[0-9]+

To ensure backwards compatibility with previous SDK versions,
the levelFrom=all now enforces categories by dominance instead of
equality. Apps with per-app and per-user categories will continue
to have selinux permissions (but not necessarily unix permissions)
to access app data with only per-user categories, but apps with only
per-user categories will not be able to access the data of apps with
both per-app and per-user categories.

Bug: 63897054
Test: Boot sailfish, run apps, verify no new selinux denials.
Test: cts-tradefed run cts -m CtsSelinuxTargetSdkCurrentTestCases
Test: cts-tradefed run cts -m CtsSelinuxTargetSdk27TestCases
Test: cts-tradefed run cts -m CtsSelinuxTargetSdk25TestCases
Test: adb sideload an OTA and verify that files are correctly labeled.
Change-Id: I64b013874fe87b55f47e817a1279e76ecf86b7c0