Run tests on iOS using Mac Catalyst and expand Apple platforms

[complexspaces]

This PR accomplishes two things:

• Compiling and running all of the tests on an iOS target, by utilizing Catalyst targets as pointed out in today's 1.82.0 release notes.
  • This is not quite as complete as if we ran these tests in a full simulator, but the environment isn't going to be that different in our use case where we are solely calling Security.framework functions. Even in the simulator, a lot of frameworks and kernel functions come "from the macOS host" anyway.
• Expanding the Apple platforms that rustls-platform-verifier can be compiled for to all available ones today.
  • AFAICT, all of the Security.framework functions we call are available everywhere and have no special OS constraints. All of them make sense to support as well:
  • visionOS is very similar to iOS and has the same networking API availability, etc.
  • watchOS has some network API constraints which restrict what you could perform TLS over, but you could still bring your own transport encryption stack as per the requirement documentation.

Closes #4 (unless anyone thinks we need the simulator explicitly)

[complexspaces]

This PR is blocked on GitHub updating their runner image to move from Rust 1.81 to 1.82 for a "stable" tier 2 Catalyst target.

[cpu]

LGTM once the runners update and CI passes. Very nice to get this coverage 🚀

[complexspaces]

The update finally rolled out so this one was ready 👍