Add parallel quorum inserts

Why it matters

This feature addresses the need for stronger write consistency guarantees by enabling quorum inserts, which ensure data is acknowledged as written only after a majority of replicas confirm the write. Executing quorum inserts in parallel improves performance and reduces write latency compared to sequential quorum inserts.

How to use it

Users can enable parallel quorum inserts by specifying the quorum setting in their insert queries or in the session settings. For example, using the setting <code>insert_quorum</code> along with <code>insert_quorum_parallel</code> set to true enables parallel quorum inserts. This ensures that the insert operation waits for confirmation from a quorum of replicas concurrently.