Change ProvisioningManager API as per review

import android.annotation.NonNull;

import android.annotation.Nullable;

import android.annotation.RequiresPermission;

import android.annotation.StringDef;

import android.annotation.SystemApi;

import android.annotation.WorkerThread;

import android.content.Context;

import com.android.internal.telephony.ITelephony;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.util.concurrent.Executor;

/**

 * Manages IMS provisioning and configuration parameters, as well as callbacks for apps to listen

 * to changes in these configurations.

 *

 * Note: IMS provisioning keys are defined per carrier or OEM using OMA-DM or other provisioning

 * applications and may vary. For compatibility purposes, the first 100 integer values used in

 * {@link #setProvisioningIntValue(int, int)} have been reserved for existing provisioning keys

 * previously defined in the Android framework. Some common constants have been defined in this

 * class to make integrating with other system apps easier. USE WITH CARE!

 * IMS provisioning keys are defined per carrier or OEM using OMA-DM or other provisioning

 * applications and may vary. It is up to the carrier and OEM applications to ensure that the

 * correct provisioning keys are being used when integrating with a vendor's ImsService.

 *

 * To avoid collisions, please use String based configurations when possible:

 * {@link #setProvisioningStringValue(int, String)} and {@link #getProvisioningStringValue(int)}.

 * Note: For compatibility purposes, the integer values [0 - 99] used in

 * {@link #setProvisioningIntValue(int, int)} have been reserved for existing provisioning keys

 * previously defined in the Android framework. Please do not redefine new provisioning keys in this

 * range or it may generate collisions with existing keys. Some common constants have also been

 * defined in this class to make integrating with other system apps easier.

 * @hide

 */

@SystemApi

public class ProvisioningManager {

    /**@hide*/

    @StringDef(prefix = "STRING_QUERY_RESULT_ERROR_", value = {

            STRING_QUERY_RESULT_ERROR_GENERIC,

            STRING_QUERY_RESULT_ERROR_NOT_READY

    })

    @Retention(RetentionPolicy.SOURCE)

    public @interface StringResultError {}

    /**

     * The query from {@link #getProvisioningStringValue(int)} has resulted in an unspecified error.

     */

     * This operation is blocking and should not be performed on the UI thread.

     *

     * @param key A String that represents the provisioning key, which is defined by the OEM.

     * @return a String value for the provided key, {@code null} if the key doesn't exist, or one

     * of the following error codes: {@link #STRING_QUERY_RESULT_ERROR_GENERIC},

     * {@link #STRING_QUERY_RESULT_ERROR_NOT_READY}.

     * @return a String value for the provided key, {@code null} if the key doesn't exist, or

     * {@link StringResultError} if there was an error getting the value for the provided key.

     * @throws IllegalArgumentException if the key provided was invalid.

     */

    @WorkerThread

    @RequiresPermission(Manifest.permission.READ_PRIVILEGED_PHONE_STATE)

    public @Nullable String getProvisioningStringValue(int key) {

    public @Nullable @StringResultError String getProvisioningStringValue(int key) {

        try {

            return getITelephony().getImsProvisioningString(mSubId, key);

        } catch (RemoteException e) {