Files in /proc/net leak information. This change is the first step in
determining which files apps may use, whitelisting benign access, and
otherwise removing access while providing safe alternative APIs.

To that end, this change:
* Introduces the proc_net_type attribute which will assigned to any
new SELinux types in /proc/net to avoid removing access to privileged
processes. These processes may be evaluated later, but are lower
priority than apps.
* Labels /proc/net/{tcp,tcp6,udp,udp6} as proc_net_vpn due to existing
use by VPN apps. This may be replaced by an alternative API.
* Audits all other proc/net access for apps.
* Audits proc/net access for other processes which are currently
granted broad read access to /proc/net but should not be including
storaged, zygote, clatd, logd, preopt2cachename and vold.

Bug: 9496886
Bug: 68016944
Test: Boot Taimen-userdebug. On both wifi and cellular: stream youtube
    navigate maps, send text message, make voice call, make video call.
    Verify no avc "granted" messages in the logs.
Test: A few VPN apps including "VPN Monster", "Turbo VPN", and
"Freighter". Verify no logspam with the current setup.
Test: atest CtsNativeNetTestCases
Test: atest netd_integration_test
Test: atest QtaguidPermissionTest
Test: atest FileSystemPermissionTest

Change-Id: I7e49f796a25cf68bc698c6c9206e24af3ae11457

On PRODUCT_FULL_TREBLE devices, non-vendor domains (except vendor
apps) are not permitted to use Binder. This commit thus:
* groups non-vendor domains using the new "coredomain" attribute,
* adds neverallow rules restricting Binder use to coredomain and
  appdomain only, and
* temporarily exempts the domains which are currently violating this
  rule from this restriction. These domains are grouped using the new
  "binder_in_vendor_violators" attribute. The attribute is needed
  because the types corresponding to violators are not exposed to the
  public policy where the neverallow rules are.

Test: mmm system/sepolicy
Test: Device boots, no new denials
Test: In Chrome, navigate to ip6.me, play a YouTube video
Test: YouTube: play a video
Test: Netflix: play a movie
Test: Google Camera: take a photo, take an HDR+ photo, record video with
      sound, record slow motion video with sound. Confirm videos play
      back fine and with sound.
Bug: 35870313
Change-Id: I0cd1a80b60bcbde358ce0f7a47b90f4435a45c95

This leaves only the existence of mdnsd domain as public API. All
other rules are implementation details of this domains's policy and
are thus now private.

Test: No change to policy according to sesearch, except for
      disappearance of all allow rules to do with mdnsd_current (as
      expected).
Bug: 31364497

Change-Id: Ia4f01d91e7d593401e8cde2d796a0f1023f6dae4

Divide policy into public and private components.  This is the first
step in splitting the policy creation for platform and non-platform
policies.  The policy in the public directory will be exported for use
in non-platform policy creation.  Backwards compatibility with it will
be achieved by converting the exported policy into attribute-based
policy when included as part of the non-platform policy and a mapping
file will be maintained to be included with the platform policy that
maps exported attributes of previous versions to the current platform
version.

Eventually we would like to create a clear interface between the
platform and non-platform device components so that the exported policy,
and the need for attributes is minimal.  For now, almost all types and
avrules are left in public.

Test: Tested by building policy and running on device.

Change-Id: Idef796c9ec169259787c3f9d8f423edf4ce27f8c