Add MediaRecorder.SystemSource.

Add an IntDef named MediaRecorder.SystemSource, which includes all
audio source that is defined in MediaRecorder.AudioSource. It can be
used for preferred device for capture preset APIs.

Test: atest AudioServiceHostTest
Bug: 180395563
Change-Id: If80a2875b64544c1e7e60999bad6dafdba712333
2 files changed