New maintenance scheme for mapping files:
Say, V is the current SELinux platform version, then at any point in time we
only maintain (V->V-1) mapping. (V->V-n) map is constructed from top (V->V-n+1)
and bottom (V-n+1->V-n) without changes to previously maintained mapping files.

Caveats:
- 26.0.cil doesn't technically represent 27.0->26.0 map, but rather
current->26.0. We'll fully migrate to the scheme with future releases.

Bug: 67510052
Test: adding new public type only requires changing the latest compat map
Change-Id: Iab5564e887ef2c8004cb493505dd56c6220c61f8

Steps taken to produce the mapping files:

1. Add prebuilts/api/28.0/[plat_pub_versioned.cil|vendor_sepolicy.cil]
from the /vendor/etc/selinux/[plat_pub_versioned.cil|vendor_sepolicy.cil]
files built on pi-dev with lunch target aosp_arm64-eng

2. Add new file private/compat/28.0/28.0.cil by doing the following:
- copy /system/etc/selinux/mapping/28.0.cil from pi-dev aosp_arm64-eng
device to private/compat/28.0/28.0.cil
- remove all attribute declaration statement (typeattribute ...) and
sort lines alphabetically
- some selinux types were added/renamed/deleted w.r.t 28 sepolicy.
Find all such types using treble_sepolicy_tests_28.0 test.
- for all these types figure out where to map them by looking at
27.0.[ignore.]cil files and add approprite entries to 28.0.[ignore.]cil.

This change also enables treble_sepolicy_tests_28.0 and install 28.0.cil
mapping onto the device.

Bug: 72458734
Test: m selinux_policy
Change-Id: I90e17c0b43af436da4b62c16179c198b5c74002c

And migrate 26.0.cil and 27.0.cil build targets from Android.mk to
Android.bp

Bug: 33691272
Test: 26.0.cil and 27.0.cil mapping files on the device are unchanged.
Change-Id: Id0ea45c149e096996bc0657615ea98915df3c9e1

Current sepolicy CIL files are built by several command-line tools
in Android.mk. This change extracts some of the build logic into a
python script to relief the effort in Android.mk.

The first command is `build_sepolicy build_cil`. It's possible to add
more sub-commands under the build_sepolicy script in the future.

Bug: 64240127
Test: build bullhead/taimen
Change-Id: Ie0ae4fc5256a550c72954cde5d5dd213a22d159a

This reverts commit 3506ad3f.
Fix angler/bullhead boot failure.

Bug: 72787689
Test: build

Current sepolicy CIL files are built by several command-line tools
in Android.mk. This change extracts some of the build logic into a
python script to relief the effort in Android.mk.

The first command is `build_sepolicy build_cil`. It's possible to add
more sub-commands under the build_sepolicy script in the future.

Bug: 64240127
Test: build and boot a device
Test: checks the content of $OUT/vendor/etc/selinux/vendor_sepolicy.cil
      is the same as before
Change-Id: I0b64f1088f413172e97b579b4f7799fa392762df