Added remove_if to priority channel

[Gibbz]

Added remove_if to priority channel. This allows removing items from the queue if there is a match in the predicate.
You can also do this on a sender, receiver and the channel directly itself.

In my sample code I use the following:

let send_ble_queue = QUEUE_CHANNEL.sender();
send_ble_queue.remove_if(|i| { i.handle == handle && i.is_single_instance() });

This is for my issue here: #3431