Swift 6, Codable, Sendable

[JoeMatt]

Add Swift 6 support, plus sendable and codable to most datatypes.

Changes:

• All Packages builds on iOS now by #if'def'ing out Process which is not available on iOS
• Added Swift 6 and 6.0 SPM values to Package.swift
• Added automatic codable and sendable conformance
• Manually added Codable support for ZipEntryInfo with the caveat that [ZipExtraField] is skipped over.

Issues:

ZipExtraField protocol not encodable. Either a need concrete types, another workaround or a way to regenerate.

[tsolomko]

Thank you for your interest in this project and your willingness to contribute. Unfortunately, I will not be accepting this PR for many reasons. Some of these reasons include:

• You're bumping the swift tools version to 6.0, while not adjusting Swift supported versions in other parts of the project and methods of distribution (Xcode project, cocoapods file).
• While trying to add support for Swift 6.0, you're not enabling testing with it in CI.
• In any case, the long-standing principle was to support as much of the past Swift versions as possible, so we will not be bumping the minimal version of Swift to 6.0 anytime soon.
• I don't understand why do we need automatic Sendable conformances in general and for this limited set of types in particular.
• I especially don't understand the need for automatic Codable conformances.
• You're if-def'ing stuff in the swcomp files, but swcomp is built on macOS only as you can see from the #if os(macOS) line in the Package.swift file.

[JoeMatt]

Take it or leave it. I needed codbale and sendable in my project to send zip status's around.

You could always make two package.swift's for 5.9 and 6.0 etc.

The ifdef's were needed because if you just open the package.swift and run tests or build against iOS it will fail in the default selection of "build package".

It's a good starting point if you ever decide you need / want these features. I'll stick to my fork I guess. Good luck.