Keeping a list of things that we need to improve to make the code more maintainable and less fragile:

• Unify kani and kani_core logic. Add intrinsics and Arbitrary support for no_core #3230 introduced duplicated logic.
• Improve contract attribute handling.
  • We cannot just blindly duplicate the attributes, and for now we specialize on a few attributes (see Fix a few issues with std verification #3255).
• Safe handling rustc ast lowering in cases where they add extra generic argument.
  • One issue we bumped into is with constant functions and feature effect enabled.
• Rename unstable function and re-add them to the kani_core::mem functions.
• Enable any_array for the standard library.