Initial sepolicy for composd

Add what we need to allow composd to run and expose an AIDL service.

Also delete the policy for compsvc; we never access it in the host
now, and the real policy is in microdroid. Retain the compos_exec
type, since it is referenced in the APEX sepolicy.

Bug: 186126194
Test: adb shell cmd -w android.system.composd; no denials.
Change-Id: I5f06b2b01852cdebd2d67009b363ec08b17ce33a
5 files changed