This PR makes the newly-added HttpTransport into expect/actual types, with a new implementation for iOS. This in turn required quite a bit of work to set up testing, and uncovered what seems to be a kotlinc type-inference bug that I've worked around here by changing the kotlin code generator a little bit.
This is rather crude, but it seems to work. Protocol and Transport are blocking APIs; in Android (and Java generally) that's okay, but Apple strongly pushes you towards async networking in iOS. So strongly in fact that all high-level APIs that are not yet deprecated are async-only, including Network.framework. This framework is also the only non-deprecated game in town when it comes to TLS.
In order to bridge the gap between Network.framework and our blocking APIs, this PR makes extensive use of dispatch semaphores - essentially, we block the calling thread until a completion handler signals the semaphore.
In the next major version of Thrifty, we should see about making the core APIs suspend, with blocking shims for migration. In that version, we can drop this charade and just use ktor or something. Until that glorious day, we get NwSocket.
Ben Bader