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.
- Refactored code from `TaskHandler` into new method `HTTPClient.Request.createRequestHead` that creates an `HTTPRequestHead` and matching `RequestFramingMetadata`
- Added required property `requestFramingMetadata` to `HTTPExecutingRequest`
- Added property `requestFramingMetadata` to `RequestBag`
Co-authored-by: Cory Benfield <lukasa@apple.com>
Motivation:
Streams length parameter is optional to allow cases were stream length is not known in advance, but we do not support this in request validation. This PR aims to address that.
Modifications:
Modifies request validation to default to chunked encoding if body length is zero or to passed in content-length header
Adds a test
Result:
Closes#218