Start handlers for new media endpoints when media resource configured (#17483)

This is in response to issue #17473. 
Not all the necessary handlers to deal with media requests are started
now when configuring synapse to use a media worker as per the [example
config](https://element-hq.github.io/synapse/latest/workers.html#synapseappmedia_repository).
The new media endpoints introduced with authenticated media fall under
the `client` & `federation` handlers in synapse.
This PR starts up handlers for the new media endpoints if a worker has
been configured with only the `media` resource type.

### Pull Request Checklist

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* [X] Pull request is based on the develop branch
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* [X] [Code
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(run the
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)

---------

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>