[cts/SettingsProvider] Readable tests for ContentResolver query/call

Tests to ensure that the result of ContentResolver query/call to list
all settings keys doesn't include hidden keys that don't have @Readable
annotation.

BUG: 208268457
Test: atest android.appsecurity.cts.ReadableSettingsFieldsTest
Change-Id: I9ac0d256dab67d986d81c7ea4ef5c4ebf1ba576b
Merged-In: I9ac0d256dab67d986d81c7ea4ef5c4ebf1ba576b
2 files changed