…proxy

When Redisson is configured with useSingleServer() pointing at a proxy
that fronts a Redis Cluster, the existing cluster-detection mechanism
(874588f) correctly sets clusterDetected=true via a Lua CROSSSLOT probe.

However, once detected, the lock renewal path (RenewalTask) switches to
the cluster branch and groups locks by slot using calcSlot(). The problem:
SingleConnectionManager never overrode calcSlot(), so it fell through to
MasterSlaveConnectionManager which always returned singleSlotRange.getStartSlot()
(effectively 0). This collapsed every lock key into slot 0, causing the
renewal to send one Lua script containing all lock keys to the proxy.
The proxy routed it to one backend node which saw keys from multiple real
cluster slots and threw CROSSSLOT -- the same error the detection was
meant to prevent.

Fix:
- Override calcSlot(String), calcSlot(byte[]) and calcSlot(ByteBuf) in
  SingleConnectionManager to compute real Redis cluster CRC16 hash-slot
  values (including hash-tag extraction) when clusterSetup is detected.
  In non-cluster single-server mode the existing behaviour (slot 0) is
  preserved.
- Extract the shared CRC16 + hash-tag slot-calculation logic into a new
  package-private helper SlotCalculator so that both
  ClusterConnectionManager and SingleConnectionManager use one canonical
  implementation with no duplication.

Tests:
- Added SlotCalculatorTest covering: null safety, plain keys, hash-tag
  extraction, invalid/edge-case tags (empty {}, unclosed brace), multiple
  brace pairs (first tag wins), cross-overload consistency (String /
  byte[] / ByteBuf produce identical slots), slot range validity [0,16384)
  and ByteBuf non-destructive read (readerIndex unchanged).
  All 29 tests pass.

Fixes: redisson#7017

Signed-off-by: Elangovan G <govansmailbox@gmail.com>
Signed-off-by: Elangovan G <eg@egP9M7G.omnissa.com>