Channel should extend Closable

[jhaye]

Is your feature request related to a problem? Please describe.

Channel currently only implements AutoClosable. It was added to the standard library as a super interface to Closable, so that everyone could benefit from the try-with-resources feature, without changing API. This also means that pretty much all APIs designed to consume something with a close method, do so via the Closable interface. Since AutoClosable is above Closable in the the hierarchy, those APIs cannot work with Channel.

Describe the solution you'd like

The Channel interface implements Closable. This extends the super interface set and is thus an API compatible change.

Describe alternatives you've considered

No response

Additional context

No response