Audio recording sources: annotate permissions

Annotate permissions for REMOTE_SUBMIX and HOTWORD.
Note that REMOTE_SUBMIX was defined before the notion
  of @SystemApi, hence its presence in SDK despite the
  need for system permission.

Bug: 72176464
Test: make online-system-api-sdk-docs
Change-Id: I315d584f06870b1e778d73a9f9415d201fe87af7