Move authenticator to its own element

In #9587 we've implemented a new `OauthAuthenticator`, which uses private key based authentication. In the current setup, we can only define one keystore. So in this case, you cannot have use a keystore for a certificate for SSL and another one for this private key.

If you take a look at the [HttpSender](https://reference.frankframework.org/#/Components/Senders/HttpSender), it has a lot of attributes to support the different kinds of authentication. At the moment, the authentication will try to pull in the underlying element. This has the drawback that you can use that for SSL certificates _OR_ to use a private key for the `PrivateKeyJwtAuthenticator`.

To make this code less obfuscated some code needs to be moved to the responsible classes. In the end we'd like to be able to have the following setup:
```

```

Start by reading the HttpSender, OauthAuthenticator, PrivateKeyJwtAuthenticator, and Keystore components referenced in the issue, along with issue #9587. Trace how authentication currently obtains the underlying Keystore; done means HttpSender can configure separate Keystore elements for SSL and PrivateKeyJwtAuthenticator as shown in the example.

Written by the indexing model from the issue text.