Motivation: The current mechanism that Kani uses for overriding std macros has proven to be very flaky, and doesn't work in some cases (e.g. #2187). We need to develop a more stable mechanism that is not prone to such issues.

Proposed change: Use the compiler driver's query mechanism to provide our own definitions of the macros, similar to how rustc handles builtin macros: https://github.com/rust-lang/rust/blob/160c2ebeca7b4e616962134f230de754fa5433b1/compiler/rustc_builtin_macros/src/lib.rs#L73.