Add global HTTP proxy to Privacy Settings page

This CL allows the user to see on the Enterprise Privacy Settings
page whether the admin set a global HTTP proxy.

Test: make RunSettingsRoboTests
Bug: 32692748

Change-Id: I3c7c46f806f39c90425fd8e098a749f3cc1e9278

src/com/android/settings/enterprise/EnterprisePrivacyFeatureProvider.java

@@ -58,4 +58,9 @@ public interface EnterprisePrivacyFeatureProvider {
      * Returns whether the Profile Owner in the managed profile (if any) set an always-on VPN.
      */
     boolean isAlwaysOnVpnSetInManagedProfile();
+
+    /**
+     * Returns whether the Device Owner set a recommended global HTTP proxy.
+     */
+    boolean isGlobalHttpProxySet();
 }