Adopt optional dependencies

Having a community repository is great for collecting options for storage, etc. The current pyproject.toml forces installation of dependencies for all existing community extras whether they are desired or not.

It would be easier to use with a pip install google-adk-community[extra-name] syntax to allow for choice of redis, open memory, etc components.

首先阅读 pyproject.toml，确定现有的 community extras 及其依赖项是如何声明的。确认可用的组件名称，然后让打包行为支持使用文档中规定的 extra 名称语法来选择组件，而不是安装所有 community 依赖项；验证所请求的 Redis 和 Open Memory 选项可以独立安装。

由索引模型根据 Issue 内容生成。