Auth UserRecord class missing passwordUpdatedAt property

* Operating System version: MacOS 3.2
* Firebase SDK version: 11.4.1
* Firebase Product: auth
* Node.js version: 18.13.0
* NPM version: 8.19.3

### [REQUIRED] Step 3: Describe the problem

#### Steps to reproduce:

The `getUser` function wraps a call to the REST API method getAccountInfo:
https://developers.google.com/resources/api-libraries/documentation/identitytoolkit/v3/python/latest/identitytoolkit_v3.relyingparty.html#getAccountInfo

That API method exposes a `passwordUpdatedAt` property. However, the Admin SDK is instantiating a UserRecord class from the response which is missing that property. This property is useful in order to track password changes (e.g., send alert email to user that password was changed).

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Trace the getUser response into the UserRecord class and compare its exposed properties with the getAccountInfo API documentation linked in the issue. Done means UserRecord exposes the passwordUpdatedAt value so callers can use it to track password changes; add or update coverage where the existing UserRecord behavior is tested.

Written by the indexing model from the issue text.