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.
## Motivation
Some of the test code was missing availability guards for Apple platforms, resulting in build failures for these platforms, e.g.
```
error: 'AsyncSequence' is only available in iOS 13.0 or newer
```
## Modifications
Add missing availability guards. I've tried to keep them as scoped as possible.
## Result
Tests can now build for run on iOS and other Apple platforms.
* Add unit tests for NWWaitingHandler
Motivation:
Closes#589. Since we already have a public initializer for
NIOTSNetworkEvents.WaitingForConnectivity, we should add unit tests for
the handler now that it's straightforward.
Modifications:
The tests are in their own file `Tests/NWWaitingHandlerTests.swift`.
* Bump swift-nio-transport-services to 1.13.0
* SwiftFormat@0.48.8
* Apply suggestions from code review
Co-authored-by: David Nadoba <dnadoba@gmail.com>
---------
Co-authored-by: David Nadoba <dnadoba@gmail.com>
Rick Newton-Rogers
Si Beaumont
Natik GadzhiandDavid Nadoba