feat(search): add bing search engine support

Integrates Bing as a new search engine option alongside existing engines like DDG, Exa, and Tavily. This provides users with more choice and improves the robustness of the web search tool.

- Adds `BingSearch` class and its integration into the `WebSurfingTool`.
- Implements the `_search_bing` async method to handle search queries via the Bing scraper.
- Updates the search strategy logic to include "bing" as an option.
- Modifies the tool cache key generation to use the file path for better uniqueness.
- Updates the configuration template to list "bing" as an available search engine.

template/bot_config_template.toml

@@ -1,5 +1,5 @@
 [inner]
-version = "6.4.0"
+version = "6.4.1"
 
 #----以下是给开发人员阅读的，如果你只是部署了麦麦，不需要阅读----
 #如果你想要修改配置文件，请递增version的值
@@ -401,7 +401,7 @@ enable_web_search_tool = true # 是否启用联网搜索tool
 enable_url_tool = true # 是否启用URL解析tool
 
 # 搜索引擎配置
-enabled_engines = ["ddg"] # 启用的搜索引擎列表，可选: "exa", "tavily", "ddg"
+enabled_engines = ["ddg"] # 启用的搜索引擎列表，可选: "exa", "tavily", "ddg","bing"
 search_strategy = "single" # 搜索策略: "single"(使用第一个可用引擎), "parallel"(并行使用所有启用的引擎), "fallback"(按顺序尝试，失败则尝试下一个)
 
 [plugins] # 插件配置