fix: improve data vendor implementations and tool signatures

- Add get_global_news for Alpha Vantage
- Fix get_insider_transactions signature (remove unused curr_date param)
- Remove unnecessary default params from API calls (sort, limit, tab)

tradingagents/dataflows/yfinance_news.py

@@ -64,7 +64,7 @@ def get_news_yfinance(
     """
     try:
         stock = yf.Ticker(ticker)
-        news = stock.get_news(count=20, tab="news")
+        news = stock.get_news(count=20)
 
         if not news:
             return f"No news found for {ticker}"