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:
frameworks/base/media/tests/MediaRouter/src/com/android/mediaroutertest/MediaRouterManagerTest.java:207: 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.
frameworks/base/media/tests/MediaRouter/src/com/android/mediaroutertest/MediaRouterManagerTest.java:239: 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.
frameworks/base/media/tests/MediaRouter/src/com/android/mediaroutertest/MediaRouterManagerTest.java:267: 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.
frameworks/base/media/tests/MediaRouter/src/com/android/mediaroutertest/MediaRouterManagerTest.java:304: 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: I56443e2fefafd6a354fcefc209643d435bfc394c