add __repr__ function to FunctionSchema for Python (#121484)
Fixes #118566
Unlike **OpOverload** or **OpOverloadPacket**, there is a lot of complex information in the schema, so for me keeping it as is is probably a good choice, but in theory the **\_\_repr__** function should show the class name as well as some other key information.
If you have any choices, please show me, thank you.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121484
Approved by: https://github.com/Skylion007
