fix minor lint error

by default just make all jetstreams to be Nackable

ensure Ack & Nack functionality is ok on jetstream

nats native solution to getting batched messages reliably

switch to a lower receive wait timeout

fix lint issues with jetstream.go

fix issue with tests related to max batch count affecting prefetching…

… message count

fix lint issues

further improve closing semantics to use the connections.Connection o…

…bject

clean lint errors