Fix Error Prone errors

Soong wasn't including android_app or android_test sources in the
javac-check target used for the Error Prone build, which allowed
some Error Prone errors to get in.  Fix them so Error Prone can be
re-enabled for these targets.

Fixes:
packages/apps/DocumentsUI/tests/unit/com/android/documentsui/base/StateTest.java:92: error: [JUnit4TestNotRun] This looks like a test method but is not run; please add @test and @Ignore, or, if this is a helper method, reduce its visibility.

Bug: 146455923
Test: m RUN_ERROR_PRONE=true javac-check
Change-Id: Ifdc8b7c0dd6dced463cf6b2c29f0abc23326a0bd