reader_consumer_v2 being a noncopyable_function imposes a restriction
when stacking one interposer consumer on top of another.
Think for example of a token-based segregator on top of a timestamp
based one.
To achieve that, the interposer consumer creator must be reentrant,
such that the consumer can be created on each "channel", but today
the creator becomes unusable after first usage.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
3dcb800a96