Mark some system intents as SystemApi

These intents are handled by some system apps and use the
android.* namespace. So mark them as SystemApi for CTS verification
purposes.

Fixes some of the CTS signature tests.

Change-Id: I18664b3e92bb24a5cf96d89cf47d6abb88b13220
Fixes: 35253923
Test: cts-tradefed run cts-dev -m CtsSignatureTestCases