Feature Request: Support for Unsized Types in kani::mem::same_allocation API

[xsxszab]

Description
The same_allocation API currently does not accept pointers to unsized types, such as dyn Trait. This feature is essential for implementing function contracts for certain pointer arithmetic operations within Rust's standard library. For example:

// library/core/src/ptr/mut_ptr.rs
impl<T: ?Sized> *mut T {
    pub const unsafe fn byte_add(self, count: usize) -> Self {
        unsafe { self.cast::<u8>().add(count).with_metadata_of(self) }
    }
}

In this case, same_allocation could be used in an ensures clause to restrict that both the input and output pointers reference the same object, like so:

#[ensures(|result| kani::mem::same_allocation(self as *const T, *result as *const T))]

However, this code currently fails to compile because T may be unsized. Extending same_allocation to handle unsized types would greatly benefit cases where function contracts contain unsized pointers.