Rationale for this change:
1) Vendors use only public files, so we should be able to use only
public cil files for compatibility test.
2) treble_sepolicy_tests_for_release.mk is too complex, because it
requires compiled sepolicy. Reducing the complexity will help migrate
into REL build.
3) This fixes a tiny bug of treble_sepolicy_tests that it can't catch
public types being moved to private types, and then removed. 29.0.cil
and 30.0.cil change contains such missing public types.
Bug: 296875906
Test: m selinux_policy (with/without intentional breakage)
Change-Id: Ia2c0733176df898f268b5680195da25b588b09c7
0d49b9bc28