Switch Allocator HAL policy to _client/_server

This switches Allocator HAL policy to the design which enables us to
identify all SELinux domains which host HALs and all domains which are
clients of HALs.

Allocator HAL is special in the sense that it's assumed to be always
binderized. As a result, rules in Camera HAL target hal_allocator_server
rather than hal_allocator (which would be the server and any client, if
the Allocator HAL runs in passthrough mode).

Test: Device boots up, no new denials
Test: YouTube video plays back
Test: Take photo using Google Camera app, recover a video, record a slow
      motion video
Bug: 34170079
Change-Id: Ifbbca554ec221712361ee6cda94c82f254d84936