Add special case for `LatestValueCache` on broadcast receivers

[shsms]

What's needed?

Broadcast channels already store the latest value on the channel, for use with the resend_latest feature.

Now that the LatestValueCache implementation is in the channels repo, it can check if a receiver is a broadcast receiver, and if so, use the broadcast channel's internal cache.

And continue to use the existing approach for other kinds of receivers.

This would improve the performance of the LatestValueCache, by eliminating the need for a task that continuously waits on a receiver for the next message.

Proposed solution

No response

Use cases

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Alternatives and workarounds

No response

Additional context

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