plugin-nats: kill()/stop() not implemented on killable/pollable tasks

Sub-issue of kestra-io/kestra-ee#10964.

**Tasks:** io.kestra.plugin.nats.core.Consume

**Why:** Long-lived NATS consume loop; no kill()/stop() to close the subscription early.

**Fix:** override `kill()` and/or `stop()` on these task classes to cancel the poll loop / close the consumer / cancel the remote job. See `io.kestra.plugin.gcp.bigquery.AbstractBigquery` for a reference implementation.

Start with io.kestra.plugin.nats.core.Consume and inspect the killable or pollable task lifecycle. Use io.kestra.plugin.gcp.bigquery.AbstractBigquery as the reference implementation, then verify that stopping or killing the task cancels the poll loop and closes the NATS consumer or remote job.

Written by the indexing model from the issue text.