Allow providers to indicate supported mime types / media types

In some contexts the media library can be opened with a media / mime type filter. Not every provider will be able to support every media type so we should filter the list of available providers depending on media type.

Proposed behaviour:

- Providers are assumed to support any media type by default
- Providers can override a method to return an array of supported mime types
- Provider should not be shown in list if it cannot provide the requested media types

Question: Should we support wild card or sub mime types like WP (sort of) does e.g. `image/*`? Would help.