Add a Natvis definition for Uuid along with tests and documentation

[ridwanabdillahi]

I'm submitting a feature

Description

This change adds Natvis visualizations for types in the uuid crate to help improve the debugging experience on Windows.

Natvis is a framework that can be used to specify how types should be viewed under a supported debugger, such as the Windows debugger (WinDbg) and the Visual Studio debugger.

The Rust compiler does have Natvis support for some types, but this is limited to some of the core libraries and not supported for external crates.

rust-lang/rfcs#3191 proposes adding support for embedding debugging visualizations such as Natvis in a Rust crate. This RFC has been approved, merged and implemented.

This PR adds:

• Natvis visualizations for the Uuid type.
• Tests for testing visualizers embedded in the uuid crate.
• A new debugger_visualizer feature for the uuid crate to enable the unstable debugger_visualizer Rust feature.
• Changes to the CI pipeline to ensure debugger visualizer tests are run and do not break silently.
• Updates to the CI pipeline to separate testing stable features vs. unstable features.

[KodrAus]

Thanks for working on this @ridwanabdillahi! This is a great PR, but I'd prefer not to add Cargo features at this stage to uuid to support nightly Rust features since we have to carry them forever, but when it stabilizes this is definitely something we should look into. So long as things don't change too much between now and then I imagine we'll be able to simply revive this PR.

[KodrAus]

It's been a while here. I don't believe we can add these because I'm not familiar enough with this infrastructure to maintain it. I would be happy to revisit this sometime in the future though.

Thanks again for the PR!