Verify the SELabels used in property_contexts

Verify that the SELabels used in property_contexts correspond to a
real type in the SEPolicy and that this type has the property_type attribute.

Bug: 74078792
Test: Build property_contexts on bullhead successfully
Test: See failure when using a faulty SELabel in property_contexts
Change-Id: If1618c2c3dae4c0cd3efa5f88056478a6db6bd0b
2 files changed