KIP-766 — fetch/findSessions queries with open endpoints for SessionStore/WindowStore

Discussion Kafka 3.1 Streams

Adds open-ended (unbounded) fetch/findSessions variants to `ReadOnlySessionStore` and `ReadOnlyWindowStore` in Kafka Streams, matching the open-ended range support added for `ReadOnlyKeyValueStore` in KIP-763. All existing session/window fetch APIs require explicit upper and lower time bounds, forcing workarounds with `Instant.MIN`/`MAX` when unbounded queries are needed.

Details