Added some testAPIs in ContentSuggestionsManager

Added the following testAPIs to replace the usage
of adb shell commands in tests:
* resetTemporaryService
* setTemporaryService
* setDefaultServiceEnabled

Bug: 180328483
Test: atest MixedProfileOwnerTest#testDisallowContentSuggestions_allowed
using the new test APIs

Change-Id: I021784d12dd784a5cef4e2c70b2fa82ca85f03f0