Update for new NIOSSL
This patch was authored and released by @gwynne.
Fix for SwiftNIOSSL 2.23.1 breaking the build of the WebSocket tests due to EVP_PKEY
no longer being visible.
Shoutout and thanks to @jhoughjr for reporting the problem!
Additional changes:
- Require Swift 5.6 (matching the rest of Vapor)
- Update CI (wouldn't be an @gwynne PR without CI tweaks!)
- Enable Concurrency back-deployment
- Normalize platform support
- Some very minor code quality cleanups
- Added several missing tests (binary frames, manual pings, automatic pings, various connect methods)