Motivation:
Moving the HTTP1ProxyConnectHandler into swift-nio-extras will make the
code which is generally useful when dealing with HTTP1 proxies available
more easily to a wider audience.
Modifications:
The code and tests are copied over from 0b5bec741b/Sources/AsyncHTTPClient/ConnectionPool/ChannelHandler/HTTP1ProxyConnectHandler.swift.
Result:
HTTP1ProxyConnectHandler will be surfaced via the NIOExtras library