fix(auth, apple): bug with cached AuthCredential, hash key was producing different value

[russellwheatley]

Description

Invoking this @([authCredential hash]) produce two different hash keys which meant we were unable to retrieve from cache if the user linkWithCredential() threw exception "credential-already-in-use" containing a credential to sign-in with.

This change ensures the same hash key is used to retrieve the exception in native code to allow signInWithCredential().

Both users confirmed it is working.

Related Issues

fixes #12931

fixes: #12944

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