Migrate legacy Jedis Cluster API to UnifiedJedis

[viktoriya-kutsarova]

Follow-up to #3315, completing the UnifiedJedis migration for the cluster path.

The cluster command callbacks were still typed over Jedis, and the node resource provider still handed out Jedis instances, which is not a UnifiedJedis subtype. This PR moves the remaining cluster internals to UnifiedJedis and removes the last uses of the deprecated sendCommand API.

Changes

• JedisClusterCommandCallback / JedisMultiKeyClusterCommandCallback now extend ClusterCommandCallback<UnifiedJedis, T> / MultiKeyClusterCommandCallback<UnifiedJedis, T>. Source-incompatible for subclasses that implemented callbacks against Jedis.
• JedisClusterNodeResourceProvider returns a UnifiedJedisAdapter wrapping the node Connection instead of Jedis.
• Commands missing on UnifiedJedis (CLUSTER *, BGREWRITEAOF, BGSAVE, SAVE, LASTSAVE, CONFIG RESETSTAT/REWRITE, TIME, CLIENT LIST/KILL, SHUTDOWN) use executeCommand(new CommandArguments(...)); all remaining sendCommand calls (deprecated since Jedis 7.4.0) are migrated as well.
• Raw command replies are decoded through JedisConverters.
• Cluster migrate now applies MigrateOption (COPY/REPLACE) via MigrateParams.
• Cluster jsonMGet routes through the typed multi-key callback using the per-node client.

Testing

Existing integration suite passes against local cluster infrastructure; no new tests.

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[viktoriya-kutsarova]

I was thinking we might also want to add a few lines in the upgrade guide regarding the change for the callbacks. If someone extended any of the callbacks, they would need to update them to use UnifiedJedis.

[[upgrading.3-to-4.jedis-cluster-callbacks]]
=== Jedis Cluster Command Callbacks

As of 4.2, `JedisClusterConnection.JedisClusterCommandCallback` and
`JedisClusterConnection.JedisMultiKeyClusterCommandCallback` extend `ClusterCommandCallback<UnifiedJedis, T>`
and `MultiKeyClusterCommandCallback<UnifiedJedis, T>` instead of their `Jedis`-typed variants.
Update custom callbacks to accept `UnifiedJedis`.
Commands without a `UnifiedJedis` method can be issued through `UnifiedJedis.executeCommand(CommandArguments)`.

[mp911de]

Thank you for your contribution. That's merged and polished now. I've updated the release notes accordingly.