Improve documentation of test configuration URLs by adding clearer
comments explaining when to use each URL configuration - Docker vs
development mode.
No functional changes, only comment improvements.
Moved ProxyConfig class from proxy_strategy.py to async_configs.py for better organization.
Improved LLM token handling with new PROVIDER_MODELS_PREFIXES.
Added test cases for deep crawling and proxy rotation.
Removed docker_config from BrowserConfig as it's handled separately.
BREAKING CHANGE: ProxyConfig import path changed from crawl4ai.proxy_strategy to crawl4ai