Add FREEZE Option to COPY Command and Explicit Transaction Management for Shard Moves

[m3hm3t]

Here's a suggested description for your PR based on the issue:

---

Description

This PR enhances shard moves and splits by adding the FREEZE option to the COPY command, reducing the need for post-operation vacuuming. To achieve this:

1. Added the FREEZE option to ConstructShardCopyStatement and LocalCopyToShard.
2. Implemented transaction management around the COPY operation.
3. Added a truncation step before COPY in ConnectToRemoteAndStartCopy to ensure the operation is within the same transaction.
4. Updated the transaction to close in ShardCopyDestReceiverShutdown.