✨ Add sync argument to deploy_index method in Matching Engine IndexEndpoint

Fixes #5304 🦕

Description

This PR introduces a new sync parameter to the deploy_index method, enabling both synchronous and asynchronous deployments. By default, the method remains synchronous to preserve backward compatibility.

Changes

• Added a sync: bool = True argument to the deploy_index method.
• If sync is True, the method waits for the long-running deployment operation (LRO) to complete before returning.
• If sync is False, the method returns immediately, and the LRO completes in the background.
• Maintains all existing behavior as default.

Usage Example

# Synchronous deployment (default behavior)
endpoint.deploy_index(index=my_index, deployed_index_id="my-index-id")

# Asynchronous deployment
endpoint.deploy_index(index=my_index, deployed_index_id="my-index-id", sync=False)

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