KIP-696 — Update Streams FSM to clarify ERROR state meaning

Accepted Kafka 2.8 Streams

Adds a `PENDING_ERROR` transient state to the `KafkaStreams` FSM with transitions `RUNNING/REBALANCING → PENDING_ERROR → ERROR`, and removes the `ERROR → PENDING_SHUTDOWN` transition to make `ERROR` a true terminal state. KIP-663 removed the automatic transition to `ERROR` when all threads die, making the original `ERROR` state definition (no threads running) ambiguous and logically inconsistent.

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