Motivation:
The tests shouldn't be making sendability violations.
Modifications:
Fix the warnings
Result:
- No warnings
- Strict concurrency is adopted!
Migrate CI to use GitHub Actions.
### Motivation:
To migrate to GitHub actions and centralised infrastructure.
### Modifications:
Changes of note:
* Adopt swift-format using rules from SwiftNIO.
* Remove scripts and docker files which are no longer needed.
* Disabled warnings-as-errors on Swift 6.0 CI pipelines for now.
### Result:
Feature parity with old CI.
SwiftNIO 2.42.0 has deprecated Lock and replaced it with a new NIOLock. This commit removes all uses of Lock and replaces them with NIOLock. Further, now, we must require SwiftNIO 2.42.0
### Motivation
With Xcode 13.2, and therefore Swift 5.5.2, Swift Concurrecy is supported on older Apple OSs. async/await suport will no longer be available on Swift before `5.5.2` but this isn't a breaking change because we have not yet made anything of it public.
### Changes
- replace all `#if compiler(>=5.5) && canImport(_Concurrency)` with `#if compiler(>=5.5.2) && canImport(_Concurrency)`
- replace all `available(macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0, *)` with `available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)`