Add tools to the default LCEL class

[vmesel]

In order to definitely migrate to LCEL syntax as the default, we need to find a simple way to encapsulate tools in LCEL, making it super agnostic and extensible.

A good API would be to have the environment variable/toml setting that holds all of the possible tools for a certain LLM and import it with the llm.bind_tools() signature from LangChain.