chore(main): release bigtable 1.52.0 - #20207

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1.52.0 (2026-08-03)

Features

• bigtable: Add AFE picker (Simple / LeastInFlight / LeastLatency) (#20204) (bcbf714)
• bigtable: Add ClientConfig.DisableSession to opt out of session backend (#20297) (7ee5e44)
• bigtable: Add getClientConfigDirectAccessChecker for session pools (#20209) (3b8d30a)
• bigtable: Add NoOpChannelPrimer for session channel pools (#20208) (d055a8a)
• bigtable: Add per-AFE sessionList for the two-tier session pool (#20224) (dbf0c3f)
• bigtable: Add protoRowToRow conversion helper for TableShim (#20257) (1297143)
• bigtable: Add Session debug surface (observability fields + methods) (#20211) (d8d3e16)
• bigtable: Add Session lifecycle (Start, Close, ForceClose, readLoop, heartBeatLoop) (#20215) (b9e53c6)
• bigtable: Add Session struct + state machine (#20117) (09acbb3)
• bigtable: Add session.Config.EnableDebug to gate sessionz debug state (#20247) (ce74c31)
• bigtable: Add SessionClient + SessionTable + lazyPool (#20228) (ab2c96c)
• bigtable: Add SessionPoolImpl (two-tier pool + scaling + debug) (#20225) (683eda8)
• bigtable: Rename session pool display to <resource-id>-<PERM> (#20248) (35e146e)
• bigtable: Route Client.Open()-returned *Table through the Diverter (#20273) (2b81c7d)
• bigtable: State-based classification for abnormal session close (#20243) (f2905b7)
• bigtable: TableShim fallback to classic on session UNIMPLEMENTED (#20269) (36540af)
• bigtable: TTL-on-idle cache for per-resource session.TableAPI (#20263) (00b2a49)
• bigtable: Wire Diverter on Client and route Open* via TableShim (#20256) (b32fbd7)

Bug Fixes

• bigtable: AFE picker latency signal — subtract poolWait and compute TransportLatency = wire − backend at source (#20281) (bb8c4d5)
• bigtable: Guard NewStream OnFinish against grpc-go double-fire (#20295) (b51da29)
• bigtable: Real per-resource pool teardown on sessionTable.Close + cache close-race gate (#20264) (599aea9)
• bigtable: Session.durations / session.uptime — set explicit histogram bucket boundaries (#20276) (97eee22)
• bigtable: SessionTableHandle self-heals across cache eviction (#20296) (0dd98cd)
• bigtable: Translate ctx errors to gRPC status on session vRPC (#20299) (0f3b2a5)
• bigtable: Treat PingAndWarm NotFound as a successful prime (#20219) (a1557ad)

Performance Improvements

• bigtable: Delete periodic Tick loop; sizing is event-driven (#20285) (2c096bd)
• bigtable: Drop pick_lost_race debug tag from CheckoutSession hot path (#20280) (bd0e400)

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