Add @UnsupportedAppUsage annotations

For packages:
  android.security
  android.service.dreams
  android.service.euicc
  android.service.vr
  android.service.wallpaper

This is an automatically generated CL. See go/UnsupportedAppUsage
for more details.

Exempted-From-Owner-Approval: Mechanical changes to the codebase
which have been approved by Android API council and announced on
android-eng@

Bug: 110868826
Test: m
Merged-In: I1c8ae08f8d3b4b2f5bf365468f22155f8def09fe
Change-Id: I09850a52193a28b0f884cfa01b564c29d25d41ed

keystore/java/android/security/Credentials.java

@@ -131,6 +131,7 @@ public class Credentials {
      * Convert objects to a PEM format which is used for
      * CA_CERTIFICATE and USER_CERTIFICATE entries.
      */
+    @UnsupportedAppUsage
     public static byte[] convertToPem(Certificate... objects)
             throws IOException, CertificateEncodingException {
         ByteArrayOutputStream bao = new ByteArrayOutputStream();

keystore/java/android/security/IKeyChainService.aidl

@@ -27,6 +27,7 @@ import android.security.keystore.ParcelableKeyGenParameterSpec;
  */
 interface IKeyChainService {
     // APIs used by KeyChain
+    @UnsupportedAppUsage
     String requestPrivateKey(String alias);
     byte[] getCertificate(String alias);
     byte[] getCaCertificates(String alias);