Bug: http://b/135139675

Coverage files are written to /data/misc/trace (governed by the
method_trace_data_file selinux type).  Allow all domains to access
(create directories, access files) this directory when native coverage
is enabled (by setting NATIVE_COVERAGE to true) in an userdebug or eng
build.

Also relax neverallow constraints to allow access to
method_trace_data_file for native coverage builds.

Test: Build 32-bit cuttlefish with coverage:
          m NATIVE_COVERAGE=true COVERAGE_PATHS="*"
      and verify that there are no selinux denials in kernel log and
      logcat.

Change-Id: I3fe7c77612854b9de7de7a0ddd5cbf44a2f5c21e
(cherry picked from commit ce9c0c5a5fbd3fda8e1fd102d2bf1ca6afebbdf9)