Add a feature to show which bugs are tracking which se denials

The feature references a new file created by the selinux make system
that is stored on device under /system/etc/selinux/ which contains a
scontext, tcontext, tclass, and the bug they map to. logd will
reference this map every time an selinux denial comes through to see if
it's a known denial with a bug attached and then add the bug number to
the denial that's logged.

go/selinux-bug-metadata

Bug: 34997782
Test: any denial -> bug map listed in the referenced file is correcty
displayed in the selinux denials that are logged

Change-Id: I75bab59917591ed700471a0b4922b5f02f86bee9