Grant record audio permission to SystemCaptionsService instead of ContentCaptureService

Now that we have a definition for a SystemCaptionsService we should move to use it instead
of piggybacking on ContentCaptureService.
This is also required to ensure that T2C will be granted audio recording permission in case it will
be shipped in a different APK for OEMs.

Test: Manual and DefaultPermissionGrantPolicyTest.
Bug: 128622041.
Change-Id: Ic0b5b21b05ff1ad200472bfc1c4eaa3c588324df