build crash_dump.policy files using Android.bp

use Android.bp instead of Android.mk to build and install the
crash_dump.policy files. This also allows mainline modules to pull
the files into their apex (dependency wasn't handled for Android.mk)

Bug: 147914640
Test: build, examine generated filesystem
Change-Id: Iae92d4f9d683ccfddf1716e7eb2877b7bff0c737