This makes the buffer/resource workers always use `replayq` for
queuing, along with collecting multiple requests in a single call.
This is done to avoid long message queues for the buffer workers and
rely on `replayq`'s capabilities of offloading to disk and detecting
overflow.
Also, this deprecates the `enable_batch` and `enable_queue` resource
creation options, as: i) queuing is now always enables; ii) batch_size
> 1 <=> batch_enabled. The corresponding metric
`dropped.queue_not_enabled` is dropped, along with `batching`. The
batching is too ephemeral, especially considering a default batch time
of 20 ms, and is not shown in the dashboard, so it was removed.
https://emqx.atlassian.net/browse/EMQX-8548
Currently, we face several issues trying to keep resource metrics
reasonable. For example, when a resource is re-created and has its
metrics reset, but then its durable queue resumes its previous work
and leads to strange (often negative) metrics.
Instead using `counters` that are shared by more than one worker to
manage gauges, we introduce an ETS table whose key is not only scoped
by the Resource ID as before, but also by the worker ID. This way,
when a worker starts/terminates, they should set their own gauges to
their values (often 0 or `replayq:count` when resuming off a queue).
With this scoping and initialization procedure, we'll hopefully avoid
hitting those strange metrics scenarios and have better control over
the gauges.
Given the implicit convention that an egress bridge containing the
`local_topic` config will forward messages without the need for a rule
action, this was added to avoid needing a rule action.
Thales Macedo Garitezi