Refactor locking mechanism to use asyncio.Lock for asynchronous container initialization

[cleemullins]

Fixes #184

[Copilot]

Pull Request Overview

This PR refactors the locking mechanism in CosmosDBStorage from threading.Lock to asyncio.Lock to properly support asynchronous container initialization, addressing issue #184.

Key Changes:

• Replaced threading.Lock with asyncio.Lock for thread-safe asynchronous operations
• Updated lock acquisition syntax from with to async with to match asyncio patterns
• Updated inline comment to reflect asynchronous context

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