Add Swift 6 features

[MatyasKriz]

This task includes bumping SwiftSyntax version (may contain breaking changes again) and implementing new features included in Swift 6 that concern either classes, protocols or method signatures, for example:

• Typed throws
• consuming
• @Sendable closure

These were taken from https://www.swift.org/blog/announcing-swift-6, if you have any more ideas on what to include, please don't hesitate to add them.

The implementation should also include tests.