unhide getId from BeginGetCredentialOption for jetpack

jetpack library needs to access the Id so it can popoulate those on
the structured begin request options.

Test: built locally
API-Coverage-Bug: 247549381

Change-Id: Iba40998751fdaa3e304f1350984cc2ba961d165f

core/api/current.txt

@@ -40265,6 +40265,7 @@ package android.service.credentials {
     ctor public BeginGetCredentialOption(@NonNull String, @NonNull String, @NonNull android.os.Bundle);
     method public int describeContents();
     method @NonNull public android.os.Bundle getCandidateQueryData();
+    method @NonNull public String getId();
     method @NonNull public String getType();
     method public void writeToParcel(@NonNull android.os.Parcel, int);
     field @NonNull public static final android.os.Parcelable.Creator<android.service.credentials.BeginGetCredentialOption> CREATOR;

core/java/android/service/credentials/BeginGetCredentialOption.java

@@ -63,8 +63,6 @@ public class BeginGetCredentialOption implements Parcelable {
      * Returns the unique id associated with this request. Providers must pass this id
      * to the constructor of {@link CredentialEntry} while creating a candidate credential
      * entry for this request option.
-     *
-     * @hide
      */
     @NonNull
     public String getId() {