As outlined in a [Swift forums post in November ’21](https://forums.swift.org/t/swiftnio-swift-version-support/53232), SwiftNIO will only support the latest non-patch Swift release and the 2 immediately prior non-patch versions.
- drop support for Swift 5.2 and 5.3.
- update CI for Swift 5.4 to run on bionic instead of focal to ensure that we still test bionic.
- add a CI job for Swift 5.7
Fabian Fett