fix: Queue batch commands to backlog during MOVED reconnection

[advaMosh]

Problem

When a MOVED-to-same-endpoint triggers reconnection (as implemented in PR #3003), batch commands (IBatch) issued during the ~50-100ms reconnection window fail immediately with RedisConnectionException: NoConnectionAvailable. This is because:

1. RedisBatch.Execute() calls SelectServer() which returns null for disconnected/reconnecting servers.
2. PhysicalBridge.TryEnqueue() returns false when !IsConnected, unlike TryWriteAsync/TryWriteSync which queue to the backlog via QueueOrFailMessage() → BacklogEnqueue().

This creates an inconsistency: individual async commands (e.g. db.StringSetAsync()) are queued and succeed after reconnection, but batch commands throw immediately during the same reconnection window.

Impact

• Applications using IBatch see 1-3 RedisConnectionException errors per MOVED redirect, while individual commands see zero errors in the same scenario

Fix

RedisBatch.Execute(): When SelectServer() returns null and BacklogPolicy.QueueWhileDisconnected is enabled, retry with allowDisconnected: true to locate the server endpoint. This mirrors the pattern already used in PrepareToPushMessageToBridge().

PhysicalBridge.TryEnqueue(): When !IsConnected || NeedsReconnect and BacklogPolicy.QueueWhileDisconnected is enabled, queue messages to the backlog instead of returning false. This matches the existing behavior of TryWriteSync() and TryWriteAsync() for individual commands.

Testing

• Before fix: 1-3 NoConnectionAvailable errors per redirect event (batch.Execute throws during ~50-100ms reconnection window)
• After fix: 0 errors — batch commands are queued to backlog and sent after reconnection completes

The fix was also validated against plain disconnect scenario, where batch commands are similarly queued rather than failing immediately.

Related

• Handle MOVED error pointing to same endpoint. #3003: Handle MOVED error pointing to same endpoint (the original MOVED reconnect fix)
• Implement connection refresh on circular moved valkey-io/valkey-glide#5893: Same fix for valkey-glide (queues commands during reconnection)
• MOVED redirects to the same endpoint are not retried #2990: Original issue report for MOVED-to-same-endpoint