Add visionOS support

[skumor-foreflight]

I am adding support for visionOS as currently Nimble will not compile for it. There is no other changes besides adding the Typealias

Waiting for this pr to be merged as well. Right now this pr has is referencing my fork of CwlPreconditionTesting with the updates.

Checklist - While not every PR needs it, new features should consider this list:

• Does this have tests?
• Does this have documentation?
• Does this break the public API (Requires major version bump)?
• Is this a new feature (Requires minor version bump)?

[younata]

This only adds support for visionOS when using SPM. Carthage won't pick this up, and people who directly embed the Nimble project (either as a git submodule/subtree, or simply downloading the code) won't pick it up either.

For carthage & people who directly embed Nimble, we need to add another framework target for visionOS (Nimble 13 will consolidate all these together). Making sure that the nimble-visionOS target/framework as marked as shared so that Carthage picks it up.

For cocoapods, I don't think we need to actually do anything here? It's worth creating a sample project and verifying that.

Regardless, I'd rather not change the upstream source for CwlPreconditionTesting, so we'll wait to merge this until your PR to them gets merged.

[skumor-foreflight]

@younata good points, I am personally only using SPM and I honestly forgot about Carthage 😅 and I also agree the upstream source should not be changed here for CwlPreconditionTesting. I thing cocoa pods should work too. I made that mainly so that our smp based project can move on and if somebody else is in need for this to compile right now and cannot wait they could use that for now.

[stonko1994]

@skumor-foreflight can we move forward with this PR and add the required changes so that it can be merged eventually? Or do you not have any plans to apply the required changes? (Otherwise, I would be open to contributing this from our fork)