does ros2_rust support autogeneration of code from .idl and .msg files, is there any example implementation to autogenerate rust nodes from .idl/.msg files?
We can generate rust code for idl and msg files thanks to the rosidl_generator_rs and rosidl_runtime_rs packages in this repo.
In the rclrs_example_msgs package, we define a few .msg files and then we consume them in message_demo example. There is nothing special about the rclrs_example_msgs package, the "magic" is in message_demo's package.xml where we specify our dependency on the rosidl_runtime_rs package.
As for the second part of your question, there is no way to generate nodes from just .idl/.msg files. To quote the ROS 2 docs
A node is a fundamental ROS 2 element that serves a single, modular purpose in a robotics system.
So having codegen for types defined in .idl/.msg files is different from automatically generating a node. You'll still need to write code that uses your auto-generated types.