gh-36760: print more information about number-field orders
Currently, the `repr()` method for orders in number fields is not very
useful: It prints the same information for all orders in a given field.
In this patch we add the generators, and, for quadratic fields, the
conductor of the order to the output of `repr()`.
URL: https://github.com/sagemath/sage/pull/36760
Reported by: Lorenz Panny
Reviewer(s): Kwankyu Lee, Lorenz Panny