sepolicy: Permission changes for new wifi mainline module

Move wifi services out of system_server into a separate APK/process.

Changes:
a) Created sepolicy for the new wifi apk.
b) The new APK will run with network_stack uid (eventually will be moved
to the same process).

Used 'audit2allow' tool to gather list of permissions required.

Note: The existing wifi related permissions in system_server is left
behind to allow the module to be loaded into system_server or
network_stack process depending on device configuration.

Bug: 113174748
Test: Device boots up and able to make wifi connection.
Test: Tested hotspot functionality.
Test: Ran WifiManagerTest & WifiSoftApTest ACTS tests locally.
Test: Will send for wifi regression tests.
Change-Id: Id19643a235bf0c28238f2729926b893ac2025b97
(cherry-picked from c7aa90091e6bec70a31a643cc4519a9a86fb0b38)
diff --git a/private/service_contexts b/private/service_contexts
index 7d6cb47..49bdb29 100644
--- a/private/service_contexts
+++ b/private/service_contexts
@@ -219,5 +219,6 @@
 wificond                                  u:object_r:wificond_service:s0
 wifiaware                                 u:object_r:wifiaware_service:s0
 wifirtt                                   u:object_r:rttmanager_service:s0
+wifi_stack                                u:object_r:wifi_stack_service:s0
 window                                    u:object_r:window_service:s0
 *                                         u:object_r:default_android_service:s0