feat(config): add streaming support and config cloning

Add streaming capability to crawler configurations and introduce clone() methods
for both BrowserConfig and CrawlerRunConfig to support immutable config updates.
Move stream parameter from arun_many() method to CrawlerRunConfig.

BREAKING CHANGE: Removed stream parameter from AsyncWebCrawler.arun_many() method.
Use config.stream=True instead.

crawl4ai/async_webcrawler.py

@@ -701,7 +701,6 @@ class AsyncWebCrawler:
         urls: List[str],
         config: Optional[CrawlerRunConfig] = None, 
         dispatcher: Optional[BaseDispatcher] = None,
-        stream: bool = False,
         # Legacy parameters maintained for backwards compatibility
         word_count_threshold=MIN_WORD_THRESHOLD,
         extraction_strategy: ExtractionStrategy = None,
@@ -723,7 +722,6 @@ class AsyncWebCrawler:
         urls: List of URLs to crawl
         config: Configuration object controlling crawl behavior for all URLs
         dispatcher: The dispatcher strategy instance to use. Defaults to MemoryAdaptiveDispatcher
-        stream: If True, returns an AsyncGenerator yielding results as they complete
         [other parameters maintained for backwards compatibility]
 
         Returns:
@@ -743,8 +741,7 @@ class AsyncWebCrawler:
         # Streaming results
         async for result in await crawler.arun_many(
             urls=["https://example1.com", "https://example2.com"],
-            config=CrawlerRunConfig(cache_mode=CacheMode.BYPASS),
-            stream=True
+            config=CrawlerRunConfig(cache_mode=CacheMode.BYPASS, stream=True),
         ):
             print(f"Processed {result.url}: {len(result.markdown)} chars")
         """
@@ -783,6 +780,8 @@ class AsyncWebCrawler:
             ) or task_result.result
         )
 
+        stream = config.stream
+        
         if stream:
             async def result_transformer():
                 async for task_result in dispatcher.run_urls_stream(crawler=self, urls=urls, config=config):