[wolf4ood]

What this PR changes/adds

• Tuning, "Task-based state machine (NATS)":
  • the new edc.nats.{tp,cn}.subscriber.workers and prefetch settings, and batch-size as the maximum per fetch;
  • sizing the datasource pool for the workers;
  • MaxAckPending must also cover the messages held by every replica.
• State machines known limitations: head-of-line blocking now applies within the limit of the workers, and
  per-participant fairness is still missing.

Why it does that

The NATS task subscribers now handle the messages with a pool of workers (eclipse-edc/Connector#6134).

Further notes

List other areas of code that have changed but are not necessarily linked to the main feature. This could be method
signature changes, package declarations, bugs that were encountered and were fixed inline, etc.

Who will sponsor this feature?

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Linked Issue(s)

Closes # <-- insert Issue number if one exists

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