[NEW PORT] lang/swift6: Powerful, flexible, multiplatform programming language (version 6)

[tagattie]

Summary

I would like to propose adding a new port for Swift 6, which is the latest version of the Swift programming language.

The announcement of Swift 6 is available at:
https://www.swift.org/blog/announcing-swift-6/

The port is needed for an upcoming port of japanese/fcitx5-hazkey.

Test Plan

Poudriere testport looks good for 150amd64 and 143amd64.

The fcitx5-hazkey port is successfully built with swift 6 and running here.