Contracts & Harnesses for swap, replace, and drop_in_place

[danielhumanmod]

Description

This PR introduces function contracts and proof harness for the NonNull pointer in the Rust core library. Specifically, it verifies three new APIs—swap, replace, and drop_in_place with Kani. These changes enhance the functionality of memory operations for NonNull pointers.

Change Overview

Covered APIs:

1. NonNull::swap: Swaps the values at two mutable locations of the same type
2. NonNull::replace: Replaces the pointer's value, returning the old value
3. NonNull::drop_in_place: Executes the destructor (if any) of the pointed-to value

Towards #53

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.

[carolynzech]

@danielhumanmod Once you finish addressing Zyad's comments, can you mark them as resolved so we know to review this again?

[Eh2406]

Thank you

[zhassan-aws]

Thanks

[danielhumanmod]

Thanks for the approval @zhassan-aws , given that all checks have been passed, do you mind helping me to start the merge process?

[zhassan-aws]

trigger approval workflow