Auto-rendering, conditional entry points, and more for LangGraph

We've made several improvements to LangGraph over the past few weeks:

• Automatic rendering of the created graph. This was a much requested community feature. You can now visualize a created graph - both in ascii and as a PNG! This will make it very easy to understand more complex graphs

• Conditional entry points. This allows you to define logic that controls how you enter into the graph. This function will be run as soon as the graph is invoked, and depending on the output you will be routed to a particular node downstream

• Prebuilt Tool Calling Executor. An off-the-shelf, prebuilt graph that uses OpenAI tool calling abilities. This makes it easy to get started with a common agent