Strengthen ptrace neverallow rules

Add additional compile time constraints on the ability to ptrace various
sensitive domains.

llkd: remove some domains which llkd should never ptrace, even on
debuggable builds, such as kernel threads and init.

crash_dump neverallows: Remove the ptrace neverallow checks because
it duplicates other neverallow assertions spread throughout the policy.

Test: policy compiles and device boots
Change-Id: Ia4240d1ce7143b983bb048e046bb4729d0af5a6e