Update Trusted Credentials screen in settings

Trusted credentials for both the primary user and its managed profiles are shown
on the Trusted Credentials fragment. All functionalities (e.g. disabling/enabling
of certificates) remain available.

Bug: 16029580

Change-Id: Ia92ae02d8c572bf4a3be172f6c255726cefc0fa1

keystore/java/android/security/KeyChain.java

@@ -397,7 +397,8 @@ public final class KeyChain {
         return KeyStore.getInstance().isHardwareBacked(algorithm);
     }
 
-    private static X509Certificate toCertificate(byte[] bytes) {
+    /** @hide */
+    public static X509Certificate toCertificate(byte[] bytes) {
         if (bytes == null) {
             throw new IllegalArgumentException("bytes == null");
         }