- Put everything in the libuv transport package under `Microsoft.AspNetCore.Server.Kestrel.Transport.Libuv.*` namespaces.
- Move stuff in Transport.Libuv/Internal/Http and Transport.Libuv/Internal/Infrastructure to Transport.Libuv/Internal (keep the Networking directory for the libuv wrappers).
- Add `Libuv` prefix to most libuv internal classes.
- Rename `KestrelEngine` to `LibuvTransport`.
- Rename `SocketOutputConsumer` to `LibuvOutputConsumer`.
- Rename `SocketOutputProducer` to `OutputProducer`.
- Fix namespaces in `Microsoft.AspNetCore.Server.Kestrel.Core.`
- Change Alloc to be a Write with a callback that exposes the WritableBuffer.
This allows the ISocketOutput to implementation to not call the callback if
the underlying socket is dead.
- Added a new functional test
- Changed socket output to be based on pipelines
- Changed connection filter glue to be based on pipelines
- Codegen that used `MemoryPoolIterator` for output now uses `WritableBuffer`
- Made `UvWriteReq` async/await friendly with `LibuvAwaitable<T>`
- Deleted MemoryPool and friends