Extract privacy item monitoring interface, add AppOpsPrivacyItemMonitor

This is to allow privacy items that aren't driven by AppOps to be added.

Changes include:
- PrivacyConfig now holds the DeviceConfig listener.
- Thread safety: currentUserId was previously accessed on multiple
  threads. All access to state of AppOpPrivacyItemMonitor is guarded by
  a lock.
- Mic/camera PrivacyItems are now filtered out and not delivered to
  PrivacyItemController callbacks. Previously, changes to the location
  app op were ignored if locationAvailable was false - but changes to
  the mic/camera app op were still processed even if micCameraAvailable
  was false (and locationAvailable was true, as otherwise the AppOps
  callback was unregistered).
  PhoneStatusBarPolicy would log a mic/camera status bar icon is visible
  regardless of micCameraAvailable if locationAvailable was true - this
  will no longer be the case.

Bug: 184629645
Test: atest CameraMicIndicatorsPermissionTest RecognitionServiceMicIndicatorTest
Test: atest AppOpsPrivacyItemMonitorTest PrivacyItemControllerTest PrivacyConfigFlagsTest
Test: m SystemUI CarSystemUI ArcSystemUI
Test: Manual, observe mic/camera privacy indicators
Change-Id: I3d78e35e1205e5ed8cc00eda71eed02f71fa35b4
Merged-In: I3d78e35e1205e5ed8cc00eda71eed02f71fa35b4