Bump Kani version to 0.32.0

[adpaco-aws]

Description of changes:

Bumps Kani version to 0.32.0 and updates the CHANGELOG.md file with the release notes. For reference, the automatically-generated notes were:

## What's Changed
* Fix dev-documentation broken link by @celinval in https://github.com/model-checking/kani/pull/2575
* Upgrade rust toolchain to nightly-2023-06-20 by @celinval in https://github.com/model-checking/kani/pull/2551
* Remove atty and tracing-tree, update hermit-abi by @karkhaz in https://github.com/model-checking/kani/pull/2581
* Automatic toolchain upgrade to nightly-2023-06-21 by @github-actions in https://github.com/model-checking/kani/pull/2582
* Add kani::spawn and an executor to the Kani library by @fzaiser in https://github.com/model-checking/kani/pull/1659
* Update rust toolchain to 2023-06-22 by @celinval in https://github.com/model-checking/kani/pull/2588
* Add "kani" configuration key to enable conditional compilation in build scripts by @celinval in https://github.com/model-checking/kani/pull/2297
* Automatic toolchain upgrade to nightly-2023-06-23 by @github-actions in https://github.com/model-checking/kani/pull/2591
* Clean up benchmark directories after building by @karkhaz in https://github.com/model-checking/kani/pull/2583
* Bump CBMC version to 5.87.0 by @adpaco-aws in https://github.com/model-checking/kani/pull/2598
* Update dependencies by @adpaco-aws in https://github.com/model-checking/kani/pull/2599
* Automatic toolchain upgrade to nightly-2023-06-24 by @github-actions in https://github.com/model-checking/kani/pull/2600
* Adds posix_memalign to the list of supported builtins by @feliperodri in https://github.com/model-checking/kani/pull/2601

## New Contributors
* @github-actions made their first contribution in https://github.com/model-checking/kani/pull/2582

**Full Changelog**: https://github.com/model-checking/kani/compare/kani-0.31.0...kani-0.32.0

Call-outs:

• Tried to collapse automatic toolchain upgrade contributions into single lines, but opted for including the last one only. Open to suggestions about that.

Testing:

• How is this change tested? Existing tests.

• Is this a refactor change? No.

Checklist

• Each commit message has a non-empty body, explaining why the change was made
• Methods or procedures are documented
• Regression or unit tests are included, or existing tests cover the modified code
• My PR is restricted to a single feature or bugfix

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

[jaisnan]

Thanks!

[karkhaz]

Upgrade rust toolchain to nightly-2023-06-20 by @celinval in #2551
Automatic toolchain upgrade to nightly-2023-06-24 by @github-actions in #2600

Do we need both of these? It might be clearer to include only the latest one?

Remove atty and tracing-tree, update hermit-abi by @karkhaz in #2581

This just removes some dependencies, I'm not sure that it's user-facing

Clean up benchmark directories after building by @karkhaz in #2583

This is benchcomp related, not user-facing