[RESTRICT AUTOMERGE] Move AudioRecordClient out of AudioPolicyService

Pull out helper classes to assist in further refactoring.

Test: Compiles
Bug: 293603271
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:370bd4b15842f5337f7c55c4cc5ba8028e92839a)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:e6b29e7a0480fb4d7e8f0c42d1b5bb440792d08f)
Merged-In: I1881c18b1ef00f3d54006349a6cf3242c747be05
Change-Id: I1881c18b1ef00f3d54006349a6cf3242c747be05